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--- libmalloc/libmalloc-521.100.59/src/magazine_tiny.c
+++ libmalloc/libmalloc-116.30.3/src/magazine_tiny.c
@@ -23,27 +23,6 @@
 
 #include "internal.h"
 
-// The address and size of the block in mag_last_free are combined. These
-// macros abstract construction of the combined value and extraction of the
-// size and pointer.
-#define TINY_MAG_LAST_FREE_FROM_PTR_AND_MSIZE(ptr, msize) (void *)(((uintptr_t)(ptr))|((msize_t)msize))
-#define TINY_PTR_FROM_MAG_LAST_FREE(x) (void *)(((uintptr_t)(x)) & ~(TINY_QUANTUM - 1))
-#define TINY_MSIZE_FROM_MAG_LAST_FREE(x) (msize_t)(((uintptr_t)(x)) & (TINY_QUANTUM - 1))
-
-// Adjusts the pointer part of mag_last_free by a given amount in bytes. Must be
-// a multiple of the quantum size (not checked).
-#define TINY_MAG_LAST_FREE_PTR_ADJUST_PTR(x, size) (x) = ((void *)(x) + (size))
-
-// Decrements the size part of mag_last_free by a given msize value. Must not
-// reduce the msize part below zero (not checked).
-#define TINY_MAG_LAST_FREE_PTR_DEC_MSIZE(x, msize_delta) (x) = ((void *)(x) - (msize_delta))
-
-static inline grain_t
-tiny_slot_from_msize(msize_t msize)
-{
-	return (!msize || (msize > NUM_TINY_SLOTS) ? NUM_TINY_SLOTS : msize - 1);
-}
-
 /*
  * Get the size of the previous free block, which is stored in the last two
  * bytes of the block.  If the previous block is not free, then the result is
@@ -55,18 +34,14 @@
 	// check whether the previous block is in the tiny region and a block header
 	// if so, then the size of the previous block is one, and there is no stored
 	// size.
-	if (ptr != TINY_REGION_HEAP_BASE(TINY_REGION_FOR_PTR(ptr))) {
+	if (ptr != TINY_REGION_FOR_PTR(ptr)) {
 		void *prev_block = (void *)((uintptr_t)ptr - TINY_QUANTUM);
 		uint32_t *prev_header = TINY_BLOCK_HEADER_FOR_PTR(prev_block);
 		msize_t prev_index = TINY_INDEX_FOR_PTR(prev_block);
 		if (BITARRAY_BIT(prev_header, prev_index)) {
 			return 1;
 		}
-		msize_t *prev_msize_ptr = &TINY_PREVIOUS_MSIZE(ptr);
-		// This is a speculative read of potentially in-use app memory, we need
-		// to use _malloc_read_uint16_via_rsp to avoid triggering warnings in
-		// memory diagnostic tools.
-		return _malloc_read_uint16_via_rsp(prev_msize_ptr);
+		return TINY_PREVIOUS_MSIZE(ptr);
 	}
 	// don't read possibly unmapped memory before the beginning of the region
 	return 0;
@@ -82,14 +57,11 @@
 	uint32_t val = (1 << (index & 31));
 
 #if DEBUG_MALLOC
-	if (msize > NUM_TINY_SLOTS) {
-		malloc_report(ASL_LEVEL_ERR, "set_tiny_meta_header_in_use() invariant broken %p %d\n", ptr, msize);
+	if (msize >= NUM_TINY_SLOTS) {
+		malloc_printf("set_tiny_meta_header_in_use() invariant broken %p %d\n", ptr, msize);
 	}
 	if ((unsigned)index + (unsigned)msize > 0x10000) {
-		malloc_report(ASL_LEVEL_ERR, "set_tiny_meta_header_in_use() invariant broken (2) %p %d\n", ptr, msize);
-	}
-	if (msize > TINY_BITMAP_RANGE_LIMIT) {
-		malloc_report(ASL_LEVEL_ERROR, "set_tiny_meta_header_in_use() invariant broken (3) %p %d\n", ptr, msize);
+		malloc_printf("set_tiny_meta_header_in_use() invariant broken (2) %p %d\n", ptr, msize);
 	}
 #endif
 
@@ -143,8 +115,8 @@
 
 		mf = get_tiny_meta_header(ptr, &ff);
 		if (msize != mf) {
-			malloc_report(ASL_LEVEL_INFO, "setting header for tiny in_use %p : %d\n", ptr, msize);
-			malloc_report(ASL_LEVEL_INFO, "reading header for tiny %p : %d %d\n", ptr, mf, ff);
+			malloc_printf("setting header for tiny in_use %p : %d\n", ptr, msize);
+			malloc_printf("reading header for tiny %p : %d %d\n", ptr, mf, ff);
 		}
 	}
 #endif
@@ -182,160 +154,6 @@
 	BITARRAY_CLR(block_header, index);
 	BITARRAY_CLR(in_use, index);
 }
-
-static MALLOC_INLINE void
-zero_tiny_free_inline_meta(void *ptr, msize_t msize)
-{
-	if (malloc_zero_policy == MALLOC_ZERO_ON_FREE) {
-		*((tiny_free_list_t *)ptr) = (tiny_free_list_t){ 0 };
-		if (msize > 1) {
-			TINY_FREE_SIZE(ptr) = 0;
-			void *follower = FOLLOWING_TINY_PTR(ptr, msize);
-			TINY_PREVIOUS_MSIZE(follower) = 0;
-		} else if (msize == 0) {
-			TINY_FREE_SIZE(ptr) = 0;
-		}
-	}
-}
-
-static MALLOC_INLINE void
-zero_tiny_free_inline_meta_following(void *ptr, msize_t msize)
-{
-	if (malloc_zero_policy == MALLOC_ZERO_ON_FREE) {
-		if (msize > 1) {
-			void *follower = FOLLOWING_TINY_PTR(ptr, msize);
-			TINY_PREVIOUS_MSIZE(follower) = 0;
-		}
-	}
-}
-
-static MALLOC_COLD MALLOC_NOINLINE void
-tiny_zero_corruption_abort(void *ptr, msize_t msize)
-{
-	uint8_t *bytes = ptr;
-	size_t size = TINY_BYTES_FOR_MSIZE(msize);
-	uint8_t *start = bytes, *end = bytes + size;
-	// scan to the first non-NUL byte
-	while (*bytes == '\0') {
-		bytes++;
-	}
-
-	unsigned int offset = (unsigned int)(bytes - start);
-	malloc_zone_error(MALLOC_ABORT_ON_CORRUPTION, true,
-			"Corruption detected in block %p of size %u at offset %u, "
-			"first 32 bytes at that offset are "
-			"%02X %02X %02X %02X %02X %02X %02X %02X | "
-			"%02X %02X %02X %02X %02X %02X %02X %02X | "
-			"%02X %02X %02X %02X %02X %02X %02X %02X | "
-			"%02X %02X %02X %02X %02X %02X %02X %02X\n",
-			ptr, (unsigned int)size, offset,
-			(bytes + 0) < end ? *(bytes + 0) : 0,
-			(bytes + 1) < end ? *(bytes + 1) : 0,
-			(bytes + 2) < end ? *(bytes + 2) : 0,
-			(bytes + 3) < end ? *(bytes + 3) : 0,
-			(bytes + 4) < end ? *(bytes + 4) : 0,
-			(bytes + 5) < end ? *(bytes + 5) : 0,
-			(bytes + 6) < end ? *(bytes + 6) : 0,
-			(bytes + 7) < end ? *(bytes + 7) : 0,
-			(bytes + 8) < end ? *(bytes + 8) : 0,
-			(bytes + 9) < end ? *(bytes + 9) : 0,
-			(bytes + 10) < end ? *(bytes + 10) : 0,
-			(bytes + 11) < end ? *(bytes + 11) : 0,
-			(bytes + 12) < end ? *(bytes + 12) : 0,
-			(bytes + 13) < end ? *(bytes + 13) : 0,
-			(bytes + 14) < end ? *(bytes + 14) : 0,
-			(bytes + 15) < end ? *(bytes + 15) : 0,
-			(bytes + 16) < end ? *(bytes + 16) : 0,
-			(bytes + 17) < end ? *(bytes + 17) : 0,
-			(bytes + 18) < end ? *(bytes + 18) : 0,
-			(bytes + 19) < end ? *(bytes + 19) : 0,
-			(bytes + 20) < end ? *(bytes + 20) : 0,
-			(bytes + 21) < end ? *(bytes + 21) : 0,
-			(bytes + 22) < end ? *(bytes + 22) : 0,
-			(bytes + 23) < end ? *(bytes + 23) : 0,
-			(bytes + 24) < end ? *(bytes + 24) : 0,
-			(bytes + 25) < end ? *(bytes + 25) : 0,
-			(bytes + 26) < end ? *(bytes + 26) : 0,
-			(bytes + 27) < end ? *(bytes + 27) : 0,
-			(bytes + 28) < end ? *(bytes + 28) : 0,
-			(bytes + 29) < end ? *(bytes + 29) : 0,
-			(bytes + 30) < end ? *(bytes + 30) : 0,
-			(bytes + 31) < end ? *(bytes + 31) : 0);
-}
-
-static MALLOC_INLINE void
-tiny_check_zero_or_clear(void *ptr, msize_t msize, boolean_t clear)
-{
-	switch (malloc_zero_policy) {
-	case MALLOC_ZERO_ON_FREE:
-		if (zero_on_free_should_sample() &&
-				_malloc_memcmp_zero_aligned8(ptr, TINY_BYTES_FOR_MSIZE(msize))) {
-			tiny_zero_corruption_abort(ptr, msize);
-		}
-		break;
-	case MALLOC_ZERO_NONE:
-		if (!clear) {
-			break;
-		}
-		// fall through
-	case MALLOC_ZERO_ON_ALLOC:
-		memset(ptr, '\0', TINY_BYTES_FOR_MSIZE(msize));
-		break;
-	}
-}
-
-// Check the inline metadata of a free block that hasn't already been verified:
-// - the previous freelist pointer
-// - agreement of the inline msizes
-//
-// Then clear all the inline metadata.
-static MALLOC_NOINLINE void
-_tiny_check_and_zero_inline_meta_from_freelist(rack_t *rack, void *ptr,
-		msize_t msize)
-{
-	tiny_free_list_t *free_ptr = ptr;
-
-	// check the previous pointer
-	(void)free_list_unchecksum_ptr(rack, &free_ptr->previous);
-	// zero both pointers
-	*free_ptr = (tiny_free_list_t){ 0 };
-
-	// check agreement between msizes and zero
-	if (msize > 1) {
-		msize_t leading_free_size = TINY_FREE_SIZE(ptr);
-		void *follower = FOLLOWING_TINY_PTR(ptr, msize);
-		msize_t trailing_free_size = TINY_PREVIOUS_MSIZE(follower);
-
-		if (leading_free_size != trailing_free_size) {
-			malloc_zone_error(MALLOC_ABORT_ON_CORRUPTION, true,
-					"Corruption of free object %p: msizes %u/%u disagree\n",
-					ptr, leading_free_size, trailing_free_size);
-		} else if (leading_free_size != msize) {
-			malloc_zone_error(MALLOC_ABORT_ON_CORRUPTION, true,
-					"Corruption at %p: unexpected msizes %u/%u\n",
-					ptr, leading_free_size, msize);
-		}
-
-		TINY_FREE_SIZE(ptr) = 0;
-		TINY_PREVIOUS_MSIZE(follower) = 0;
-	} else if (msize == 0 && TINY_FREE_SIZE(ptr) != 0) {
-		malloc_zone_error(MALLOC_ABORT_ON_CORRUPTION, true,
-				"Corruption at %p: unexpected nonzero msize %u\n", ptr,
-				TINY_FREE_SIZE(ptr));
-	}
-}
-
-static MALLOC_ALWAYS_INLINE MALLOC_INLINE void
-tiny_check_and_zero_inline_meta_from_freelist(rack_t *rack, void *ptr,
-		msize_t msize)
-{
-	if (malloc_zero_policy != MALLOC_ZERO_ON_FREE) {
-		return;
-	}
-
-	_tiny_check_and_zero_inline_meta_from_freelist(rack, ptr, msize);
-}
-
 
 static MALLOC_INLINE void
 set_tiny_meta_header_free(const void *ptr, msize_t msize)
@@ -348,7 +166,7 @@
 
 #if DEBUG_MALLOC
 	if ((unsigned)index + (unsigned)msize > 0x10000) {
-		malloc_report(ASL_LEVEL_ERR, "setting header for tiny free %p msize too large: %d\n", ptr, msize);
+		malloc_printf("setting header for tiny free %p msize too large: %d\n", ptr, msize);
 	}
 #endif
 
@@ -371,8 +189,8 @@
 	boolean_t ff;
 	msize_t mf = get_tiny_meta_header(ptr, &ff);
 	if ((msize != mf) || !ff) {
-		malloc_report(ASL_LEVEL_INFO, "setting header for tiny free %p : %u\n", ptr, msize);
-		malloc_report(ASL_LEVEL_INFO, "reading header for tiny %p : %u %u\n", ptr, mf, ff);
+		malloc_printf("setting header for tiny free %p : %u\n", ptr, msize);
+		malloc_printf("reading header for tiny %p : %u %u\n", ptr, mf, ff);
 	}
 #endif
 }
@@ -416,7 +234,7 @@
 	}
 
 	previous_index = index - previous_msize;
-	previous_ptr = TINY_PTR_FOR_INDEX(previous_index, TINY_REGION_FOR_PTR(ptr));
+	previous_ptr = (void *)((uintptr_t)TINY_REGION_FOR_PTR(ptr) + TINY_BYTES_FOR_MSIZE(previous_index));
 	if (!BITARRAY_BIT(block_header, previous_index)) {
 		return NULL;
 	}
@@ -430,72 +248,6 @@
 	// conservative check did match true check
 	*prev_msize = previous_msize;
 	return previous_ptr;
-}
-
-// Given a region and a slot index, scans regions that precede the region on
-// the magazine region list for one that has something on its free list for
-// the given slot and returns the address of the last such block, or NULL if
-// there is none. To reduce overhead, we scan forward from the first region
-// looking for our region and noting the last on the freelist for the given slot
-// for each earlier region, stopping once we have looked at 5 regions if we did
-// not reach our own. This has the effect of keeping the blocks for early
-// regions near the front of the freelist while not spending large amounts of
-// time looking for the "best" place to put this region's free blocks when there
-// are many regions in the magazine.
-static MALLOC_INLINE void *
-tiny_earlier_region_last_free(magazine_t *tiny_mag_ptr,
-		region_trailer_t *trailer, grain_t slot)
-{
-	int count = 0;
-	uint16_t target_block = 0;
-	region_trailer_t *target_trailer = NULL;
-	region_trailer_t *next_trailer = tiny_mag_ptr->firstNode;
-
-	while (next_trailer && next_trailer != trailer && count++ < 5) {
-		tiny_region_t r = TINY_REGION_FOR_PTR(next_trailer);
-		uint16_t block = r->free_blocks_by_slot[slot].last_block;
-		if (block) {
-			target_block = block;
-			target_trailer = next_trailer;
-		}
-		next_trailer = next_trailer->next;
-	}
-	return target_block ? TINY_PTR_FOR_INDEX(target_block - 1,
-			TINY_REGION_FOR_PTR(target_trailer)) : NULL;
-}
-
-static MALLOC_INLINE void
-tiny_update_region_free_list_for_remove(grain_t slot, tiny_free_list_t *ptr,
-		tiny_free_list_t *new_head)
-{
-	uint16_t ptr_index = TINY_INDEX_FOR_PTR(ptr);
-	tiny_region_t ptr_region = TINY_REGION_FOR_PTR(ptr);
-	region_free_blocks_t *blocks = &ptr_region->free_blocks_by_slot[slot];
-	MALLOC_ASSERT(ptr_index == blocks->first_block - 1);
-
-	if (new_head && (TINY_REGION_FOR_PTR(new_head) == TINY_REGION_FOR_PTR(ptr))) {
-		uint16_t new_head_block = TINY_INDEX_FOR_PTR(new_head) + 1;
-		if (blocks->first_block == blocks->last_block) {
-			blocks->last_block = new_head_block;
-		}
-		blocks->first_block = new_head_block;
-	} else {
-		// No more entries in this region.
-		blocks->first_block = blocks->last_block = 0;
-	}
-}
-
-void
-tiny_print_region_free_list(void *ptr, grain_t slot)
-{
-	tiny_region_t region = TINY_REGION_FOR_PTR(ptr);
-	region_free_blocks_t *blocks = &region->free_blocks_by_slot[slot];
-	malloc_printf("For region %p, first block: %d (%p), last block: %d (%p)\n",
-			region,
-			blocks->first_block,
-			blocks->first_block ? TINY_PTR_FOR_INDEX(blocks->first_block - 1, region) : (void *)0,
-			blocks->last_block,
-			blocks->last_block ? TINY_PTR_FOR_INDEX(blocks->last_block - 1, region) : (void *)0);
 }
 
 /*
@@ -504,105 +256,40 @@
  * Assumes szone has been locked
  */
 static void
-tiny_free_list_add_ptr(rack_t *rack, magazine_t *tiny_mag_ptr, void *ptr, msize_t msize)
-{
-	grain_t slot = (!msize || (msize > NUM_TINY_SLOTS)) ? NUM_TINY_SLOTS : msize - 1;
+tiny_free_list_add_ptr(szone_t *szone, magazine_t *tiny_mag_ptr, void *ptr, msize_t msize)
+{
+	grain_t slot = (!msize || (msize >= NUM_TINY_SLOTS)) ? NUM_TINY_SLOTS - 1 : msize - 1;
 	tiny_free_list_t *free_ptr = ptr;
 	tiny_free_list_t *free_head = tiny_mag_ptr->mag_free_list[slot].p;
 
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
+		malloc_printf("in %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
 	}
 	if (((uintptr_t)ptr) & (TINY_QUANTUM - 1)) {
-		malloc_zone_error(rack->debug_flags, true, "tiny_free_list_add_ptr: Unaligned ptr: %p\n", ptr);
+		szone_error(szone, 1, "tiny_free_list_add_ptr: Unaligned ptr", ptr, NULL);
 	}
 #endif
 	set_tiny_meta_header_free(ptr, msize);
 	if (free_head) {
 #if DEBUG_MALLOC
 		if (free_list_unchecksum_ptr(szone, &free_head->previous)) {
-			malloc_zone_error(rack->debug_flags, true,
-					"tiny_free_list_add_ptr: Internal invariant broken (free_head->previous): "
-					"ptr=%p slot=%d free_head=%p previous=%p\n", ptr, slot, (void *)free_head, free_head->previous.p);
+			szone_error(szone, 1, "tiny_free_list_add_ptr: Internal invariant broken (free_head->previous)", ptr,
+						"ptr=%p slot=%d free_head=%p previous=%p\n", ptr, slot, (void *)free_head, free_head->previous.p);
 		}
 		if (!tiny_meta_header_is_free(free_head)) {
-			malloc_zone_error(rack->debug_flags, true,
-					"tiny_free_list_add_ptr: Internal invariant broken (free_head is not a free pointer): "
-					"ptr=%p slot=%d free_head=%p\n", ptr, slot, (void *)free_head);
-		}
-#endif
+			szone_error(szone, 1, "tiny_free_list_add_ptr: Internal invariant broken (free_head is not a free pointer)", ptr,
+						"ptr=%p slot=%d free_head=%p\n", ptr, slot, (void *)free_head);
+		}
+#endif
+		free_head->previous.u = free_list_checksum_ptr(szone, free_ptr);
 	} else {
 		BITMAPV_SET(tiny_mag_ptr->mag_bitmap, slot);
 	}
-
-	tiny_region_t region = TINY_REGION_FOR_PTR(ptr);
-	region_free_blocks_t *free_blocks = &region->free_blocks_by_slot[slot];
-	uint16_t first_free_block_index = free_blocks->first_block;
-	uint16_t this_block_index = TINY_INDEX_FOR_PTR(ptr);
-
-	if (first_free_block_index) {
-		// This region already has something on its free list.
-		tiny_free_list_t *old_first_free = TINY_PTR_FOR_INDEX(first_free_block_index - 1, region);
-		tiny_free_list_t *prev_ptr = free_list_unchecksum_ptr(rack, &old_first_free->previous);
-		if (!prev_ptr) {
-			// Old first item was the first item in the magazine free list -
-			// update the magazine head pointer to point to this block.
-			tiny_mag_ptr->mag_free_list[slot].p = free_ptr;
-		} else {
-			prev_ptr->next.u = free_list_checksum_ptr(rack, free_ptr); // XXX
-		}
-
-		// Set our previous pointer to the one from the old first block.
-		// It's already checksummed, so just copy it directly. It is NULL if
-		// the old first block was also the first block on the magazine free
-		// list.
-		free_ptr->previous.u = old_first_free->previous.u;
-
-		// Our "next" pointer always points to the block that used to be first
-		// and we are always its predecessor.
-		free_ptr->next.u = free_list_checksum_ptr(rack, old_first_free);
-		old_first_free->previous.u = free_list_checksum_ptr(rack, free_ptr);
-
-		// Update the first free block index for this region.
-		free_blocks->first_block = this_block_index + 1;
-	} else {
-		// Free list for this region is empty. Add ourselves to the magazine
-		// free list between the last block of the preceding region that has
-		// a free block and the first block of the next region with a free
-		// block (either of which may not exist).
-		tiny_free_list_t *prev_free = NULL;
-		tiny_free_list_t *next_free;
-
-		// If the magazine free list is empty, we know we are going to add at
-		// the front. Otherwise, find the correct place. If we are freeing to
-		// the recirc depot, we can always free to the front because we don't
-		// care about ordering in the depot (since no allocations occur there).
-		mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(region);
-		if (mag_index != DEPOT_MAGAZINE_INDEX
-				&& tiny_mag_ptr->mag_free_list[slot].p) {
-			region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(region);
-			prev_free = tiny_earlier_region_last_free(tiny_mag_ptr, trailer, slot);
-		}
-		if (!prev_free) {
-			// We are becoming the head of the magazine free list.
-			next_free = tiny_mag_ptr->mag_free_list[slot].p;
-			tiny_mag_ptr->mag_free_list[slot].p = free_ptr;
-		} else {
-			next_free = free_list_unchecksum_ptr(rack, &prev_free->next);
-			prev_free->next.u = free_list_checksum_ptr(rack, free_ptr);
-		}
-		free_ptr->previous.u = free_list_checksum_ptr(rack, prev_free);
-
-		if (next_free) {
-			next_free->previous.u = free_list_checksum_ptr(rack, free_ptr);
-		}
-		free_ptr->next.u = free_list_checksum_ptr(rack, next_free);
-
-		// Set the first and last free block index for this region.
-		free_blocks->first_block = free_blocks->last_block =
-				this_block_index + 1;
-	}
+	free_ptr->previous.u = free_list_checksum_ptr(szone, NULL);
+	free_ptr->next.u = free_list_checksum_ptr(szone, free_head);
+
+	tiny_mag_ptr->mag_free_list[slot].p = free_ptr;
 }
 
 /*
@@ -610,27 +297,26 @@
  * Assumes szone has been locked
  */
 static void
-tiny_free_list_remove_ptr(rack_t *rack, magazine_t *tiny_mag_ptr, void *ptr, msize_t msize)
-{
-	grain_t slot = tiny_slot_from_msize(msize);
+tiny_free_list_remove_ptr(szone_t *szone, magazine_t *tiny_mag_ptr, void *ptr, msize_t msize)
+{
+	grain_t slot = (!msize || (msize >= NUM_TINY_SLOTS)) ? NUM_TINY_SLOTS - 1 : msize - 1;
 	tiny_free_list_t *free_ptr = ptr, *next, *previous;
 
-	next = free_list_unchecksum_ptr(rack, &free_ptr->next);
-	previous = free_list_unchecksum_ptr(rack, &free_ptr->previous);
+	next = free_list_unchecksum_ptr(szone, &free_ptr->next);
+	previous = free_list_unchecksum_ptr(szone, &free_ptr->previous);
 
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "In %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
+		malloc_printf("In %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
 	}
 #endif
 	if (!previous) {
 		// The block to remove is the head of the free list
 #if DEBUG_MALLOC
 		if (tiny_mag_ptr->mag_free_list[slot] != ptr) {
-			malloc_zone_error(rack->debug_flags, true,
-					"tiny_free_list_remove_ptr: Internal invariant broken (tiny_mag_ptr->mag_free_list[slot]): "
-					"ptr=%p slot=%d msize=%d tiny_mag_ptr->mag_free_list[slot]=%p\n", ptr, slot, msize,
-					(void *)tiny_mag_ptr->mag_free_list[slot]);
+			szone_error(szone, 1, "tiny_free_list_remove_ptr: Internal invariant broken (tiny_mag_ptr->mag_free_list[slot])", ptr,
+						"ptr=%p slot=%d msize=%d tiny_mag_ptr->mag_free_list[slot]=%p\n", ptr, slot, msize,
+						(void *)tiny_mag_ptr->mag_free_list[slot]);
 			return;
 		}
 #endif
@@ -639,55 +325,19 @@
 			BITMAPV_CLR(tiny_mag_ptr->mag_bitmap, slot);
 		}
 	} else {
-		// Check that the next pointer of "previous" points to free_ptr.
-		tiny_free_list_t *prev_next = free_list_unchecksum_ptr(rack, &previous->next);
-		if (prev_next != free_ptr) {
-			malloc_zone_error(rack->debug_flags, true,
-					"tiny_free_list_remove_ptr: Internal invariant broken (next ptr of prev): "
-					"ptr=%p, prev_next=%p\n", ptr, prev_next);
-			__builtin_unreachable(); // Always crashes in malloc_zone_error().
-		}
-
 		// We know free_ptr is already checksummed, so we don't need to do it
 		// again.
 		previous->next = free_ptr->next;
 	}
 	if (next) {
-		// Check that the previous pointer of "next" points to free_ptr.
-		tiny_free_list_t *next_prev = free_list_unchecksum_ptr(rack, &next->previous);
-		if (next_prev != free_ptr) {
-			malloc_zone_error(rack->debug_flags, true,
-					"tiny_free_list_remove_ptr: Internal invariant broken (prev ptr of next): "
-					"ptr=%p, next_prev=%p\n", ptr, next_prev);
-			__builtin_unreachable(); // Always crashes in malloc_zone_error().
-		}
-
 		// We know free_ptr is already checksummed, so we don't need to do it
 		// again.
 		next->previous = free_ptr->previous;
 	}
-
-	tiny_region_t region = TINY_REGION_FOR_PTR(ptr);
-	region_free_blocks_t *free_blocks = &region->free_blocks_by_slot[slot];
-	uint16_t this_block_index = TINY_INDEX_FOR_PTR(ptr);
-
-	boolean_t is_first = free_blocks->first_block == this_block_index + 1;
-	boolean_t is_last = free_blocks->last_block == this_block_index + 1;
-
-	if (is_first && is_last) {
-		// Removing the one and only item on the list. Set both block indices to 0.
-		free_blocks->first_block = free_blocks->last_block = 0;
-	} else if (is_first) {
-		MALLOC_ASSERT(next);
-		free_blocks->first_block = TINY_INDEX_FOR_PTR(next) + 1;
-	} else if (is_last) {
-		MALLOC_ASSERT(previous);
-		free_blocks->last_block	= TINY_INDEX_FOR_PTR(previous) + 1;
-	}
 }
 
 void
-tiny_finalize_region(rack_t *rack, magazine_t *tiny_mag_ptr)
+tiny_finalize_region(szone_t *szone, magazine_t *tiny_mag_ptr)
 {
 	void *last_block, *previous_block;
 	uint32_t *last_header;
@@ -705,7 +355,7 @@
 	//
 
 	if (tiny_mag_ptr->mag_bytes_free_at_end) {
-		last_block = (void *)((uintptr_t)TINY_REGION_HEAP_END(tiny_mag_ptr->mag_last_region) - tiny_mag_ptr->mag_bytes_free_at_end);
+		last_block = (void *)((uintptr_t)TINY_REGION_END(tiny_mag_ptr->mag_last_region) - tiny_mag_ptr->mag_bytes_free_at_end);
 		last_msize = TINY_MSIZE_FOR_BYTES(tiny_mag_ptr->mag_bytes_free_at_end);
 		last_header = TINY_BLOCK_HEADER_FOR_PTR(last_block);
 		last_index = TINY_INDEX_FOR_PTR(last_block);
@@ -727,23 +377,20 @@
 		previous_block = tiny_previous_preceding_free(last_block, &previous_msize);
 		if (previous_block) {
 			set_tiny_meta_header_middle(last_block);
-			tiny_free_list_remove_ptr(rack, tiny_mag_ptr, previous_block, previous_msize);
-			// zero out the trailing inline msize of the previous block to
-			// connect its zero prefix to the last block
-			zero_tiny_free_inline_meta_following(previous_block, previous_msize);
+			tiny_free_list_remove_ptr(szone, tiny_mag_ptr, previous_block, previous_msize);
 			last_block = previous_block;
 			last_msize += previous_msize;
 		}
 
 		// splice last_block into the free list
-		tiny_free_list_add_ptr(rack, tiny_mag_ptr, last_block, last_msize);
+		tiny_free_list_add_ptr(szone, tiny_mag_ptr, last_block, last_msize);
 		tiny_mag_ptr->mag_bytes_free_at_end = 0;
 	}
 
 #if CONFIG_ASLR_INTERNAL
 	// Coalesce the big free block at start with any following free blocks
 	if (tiny_mag_ptr->mag_bytes_free_at_start) {
-		last_block = TINY_REGION_HEAP_BASE(tiny_mag_ptr->mag_last_region);
+		last_block = TINY_REGION_ADDRESS(tiny_mag_ptr->mag_last_region);
 		last_msize = TINY_MSIZE_FOR_BYTES(tiny_mag_ptr->mag_bytes_free_at_start);
 
 		void *next_block = (void *)((uintptr_t)last_block + tiny_mag_ptr->mag_bytes_free_at_start);
@@ -755,15 +402,12 @@
 		if (tiny_meta_header_is_free(next_block)) {
 			msize_t next_msize = get_tiny_free_size(next_block);
 			set_tiny_meta_header_middle(next_block);
-			tiny_free_list_remove_ptr(rack, tiny_mag_ptr, next_block, next_msize);
-			// zero inline metadata of next_block to continue the zero prefix of
-			// the big starting free block
-			zero_tiny_free_inline_meta(next_block, next_msize);
+			tiny_free_list_remove_ptr(szone, tiny_mag_ptr, next_block, next_msize);
 			last_msize += next_msize;
 		}
 
 		// splice last_block into the free list
-		tiny_free_list_add_ptr(rack, tiny_mag_ptr, last_block, last_msize);
+		tiny_free_list_add_ptr(szone, tiny_mag_ptr, last_block, last_msize);
 		tiny_mag_ptr->mag_bytes_free_at_start = 0;
 	}
 #endif
@@ -772,14 +416,14 @@
 }
 
 int
-tiny_free_detach_region(rack_t *rack, magazine_t *tiny_mag_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)TINY_REGION_HEAP_BASE(r);
+tiny_free_detach_region(szone_t *szone, magazine_t *tiny_mag_ptr, region_t r)
+{
+	uintptr_t start = (uintptr_t)TINY_REGION_ADDRESS(r);
 	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)TINY_REGION_HEAP_END(r);
+	uintptr_t limit = (uintptr_t)TINY_REGION_END(r);
 	boolean_t is_free;
 	msize_t msize;
-	region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(r);
+	int total_alloc = 0;
 
 	while (current < limit) {
 		msize = get_tiny_meta_header((void *)current, &is_free);
@@ -789,27 +433,29 @@
 		}
 		if (!msize) {
 #if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "*** tiny_free_detach_region error with %p: msize=%d is_free=%d\n", (void *)current, msize, is_free);
+			malloc_printf("*** tiny_free_detach_region error with %p: msize=%d is_free =%d\n", (void *)current, msize, is_free);
 #endif
 			break;
 		}
 		if (is_free) {
-			tiny_free_list_remove_ptr(rack, tiny_mag_ptr, (void *)current, msize);
+			tiny_free_list_remove_ptr(szone, tiny_mag_ptr, (void *)current, msize);
+		} else {
+			total_alloc++;
 		}
 		current += TINY_BYTES_FOR_MSIZE(msize);
 	}
-	return trailer->objects_in_use;
+	return total_alloc;
 }
 
 size_t
-tiny_free_reattach_region(rack_t *rack, magazine_t *tiny_mag_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)TINY_REGION_HEAP_BASE(r);
+tiny_free_reattach_region(szone_t *szone, magazine_t *tiny_mag_ptr, region_t r)
+{
+	uintptr_t start = (uintptr_t)TINY_REGION_ADDRESS(r);
 	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)TINY_REGION_HEAP_END(r);
+	uintptr_t limit = (uintptr_t)TINY_REGION_END(r);
 	boolean_t is_free;
 	msize_t msize;
-	size_t bytes_used = REGION_TRAILER_FOR_TINY_REGION(r)->bytes_used;
+	size_t total_alloc = 0;
 
 	while (current < limit) {
 		msize = get_tiny_meta_header((void *)current, &is_free);
@@ -819,16 +465,18 @@
 		}
 		if (!msize) {
 #if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "*** tiny_free_reattach_region error with %p: msize=%d is_free=%d\n", (void *)current, msize, is_free);
+			malloc_printf("*** tiny_free_reattach_region error with %p: msize=%d is_free =%d\n", (void *)current, msize, is_free);
 #endif
 			break;
 		}
 		if (is_free) {
-			tiny_free_list_add_ptr(rack, tiny_mag_ptr, (void *)current, msize);
+			tiny_free_list_add_ptr(szone, tiny_mag_ptr, (void *)current, msize);
+		} else {
+			total_alloc += TINY_BYTES_FOR_MSIZE(msize);
 		}
 		current += TINY_BYTES_FOR_MSIZE(msize);
 	}
-	return bytes_used;
+	return total_alloc;
 }
 
 typedef struct {
@@ -836,14 +484,14 @@
 } tiny_pg_pair_t;
 
 void
-tiny_free_scan_madvise_free(rack_t *rack, magazine_t *depot_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)TINY_REGION_HEAP_BASE(r);
+tiny_free_scan_madvise_free(szone_t *szone, magazine_t *depot_ptr, region_t r)
+{
+	uintptr_t start = (uintptr_t)TINY_REGION_ADDRESS(r);
 	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)TINY_REGION_HEAP_END(r);
+	uintptr_t limit = (uintptr_t)TINY_REGION_END(r);
 	boolean_t is_free;
 	msize_t msize;
-	tiny_pg_pair_t advisory[((TINY_HEAP_SIZE + vm_kernel_page_size - 1) >> vm_kernel_page_shift) >>
+	tiny_pg_pair_t advisory[((TINY_REGION_PAYLOAD_BYTES + vm_page_quanta_size - 1) >> vm_page_quanta_shift) >>
 							1]; // 256bytes stack allocated
 	int advisories = 0;
 
@@ -854,7 +502,7 @@
 		if (is_free && !msize && (current == start)) {
 			// first block is all free
 #if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_INFO, "*** tiny_free_scan_madvise_free first block is all free! %p: msize=%d is_free=%d\n", (void *)current,
+			malloc_printf("*** tiny_free_scan_madvise_free first block is all free! %p: msize=%d is_free =%d\n", (void *)current,
 						  msize, is_free);
 #endif
 			uintptr_t pgLo = round_page_kernel(start + sizeof(tiny_free_list_t) + sizeof(msize_t));
@@ -869,7 +517,7 @@
 		}
 		if (!msize) {
 #if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "*** tiny_free_scan_madvise_free error with %p: msize=%d is_free=%d\n", (void *)current, msize, is_free);
+			malloc_printf("*** tiny_free_scan_madvise_free error with %p: msize=%d is_free =%d\n", (void *)current, msize, is_free);
 #endif
 			break;
 		}
@@ -878,7 +526,7 @@
 			uintptr_t pgHi = trunc_page_kernel(current + TINY_BYTES_FOR_MSIZE(msize) - sizeof(msize_t));
 
 			if (pgLo < pgHi) {
-				advisory[advisories].pnum = (pgLo - (uintptr_t)r) >> vm_kernel_page_shift;
+				advisory[advisories].pnum = (pgLo - start) >> vm_kernel_page_shift;
 				advisory[advisories].size = (pgHi - pgLo) >> vm_kernel_page_shift;
 				advisories++;
 			}
@@ -897,24 +545,23 @@
 		// (1) is ensured by design, (2) and (3) are ensured by bumping the globally visible counter node->pinned_to_depot.
 
 		OSAtomicIncrement32Barrier(&(REGION_TRAILER_FOR_TINY_REGION(r)->pinned_to_depot));
-		SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, depot_ptr);
 		for (i = 0; i < advisories; ++i) {
-			uintptr_t addr = (advisory[i].pnum << vm_kernel_page_shift) + (uintptr_t)r;
+			uintptr_t addr = (advisory[i].pnum << vm_kernel_page_shift) + start;
 			size_t size = advisory[i].size << vm_kernel_page_shift;
 
-			mvm_madvise_free(rack, r, addr, addr + size, NULL, rack->debug_flags & MALLOC_DO_SCRIBBLE);
-		}
-		SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
+			madvise_free_range(szone, r, addr, addr + size, NULL);
+		}
+		SZONE_MAGAZINE_PTR_LOCK(szone, depot_ptr);
 		OSAtomicDecrement32Barrier(&(REGION_TRAILER_FOR_TINY_REGION(r)->pinned_to_depot));
 	}
 }
 
-#if CONFIG_RECIRC_DEPOT
 static region_t
-tiny_find_msize_region(rack_t *rack, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
+tiny_find_msize_region(szone_t *szone, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
 {
 	tiny_free_list_t *ptr;
-	grain_t slot = tiny_slot_from_msize(msize);
+	grain_t slot = msize - 1;
 	free_list_t *free_list = tiny_mag_ptr->mag_free_list;
 	free_list_t *the_slot = free_list + slot;
 	free_list_t *limit;
@@ -945,7 +592,7 @@
 	}
 
 	slot = BITMAPV_CTZ(bitmap);
-	limit = free_list + NUM_TINY_SLOTS;
+	limit = free_list + NUM_TINY_SLOTS - 1;
 	free_list += slot;
 
 	if (free_list < limit) {
@@ -955,13 +602,13 @@
 		} else {
 			/* Shouldn't happen. Fall through to look at last slot. */
 #if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "in tiny_find_msize_region(), mag_bitmap out of sync, slot=%d\n", slot);
+			malloc_printf("in tiny_find_msize_region(), mag_bitmap out of sync, slot=%d\n", slot);
 #endif
 		}
 	}
 
 	// We are now looking at the last slot, which contains blocks equal to, or
-	// due to coalescing of free blocks, larger than NUM_TINY_SLOTS * tiny quantum size.
+	// due to coalescing of free blocks, larger than (NUM_TINY_SLOTS - 1) * tiny quantum size.
 	ptr = limit->p;
 	if (ptr) {
 		return TINY_REGION_FOR_PTR(ptr);
@@ -969,110 +616,9 @@
 
 	return NULL;
 }
-#endif // CONFIG_RECIRC_DEPOT
-
-#if CONFIG_MADVISE_PRESSURE_RELIEF
-void
-tiny_madvise_pressure_relief(rack_t *rack)
-{
-	mag_index_t mag_index;
-	magazine_t *tiny_depot_ptr = (&rack->magazines[DEPOT_MAGAZINE_INDEX]);
-
-	for (mag_index = 0; mag_index < rack->num_magazines; mag_index++) {
-		size_t index;
-		for (index = 0; index < rack->region_generation->num_regions_allocated; ++index) {
-			rack_region_lock(rack);
-
-			region_t tiny = rack->region_generation->hashed_regions[index];
-			if (!tiny || tiny == HASHRING_REGION_DEALLOCATED) {
-				rack_region_unlock(rack);
-				continue;
-			}
-
-			region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(tiny);
-			// Make sure that the owning magazine doesn't try and take this out
-			// from under our feet.
-			trailer->dispose_flags |= RACK_DISPOSE_DELAY;
-			rack_region_unlock(rack);
-
-			magazine_t *mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-					trailer, MAGAZINE_INDEX_FOR_TINY_REGION(tiny));
-
-			// If acquiring the region lock was enough to prevent the owning
-			// magazine from deallocating the region, free it now so we don't
-			// do wasted work.
-			if (rack_region_maybe_dispose(rack, tiny, TINY_REGION_SIZE, trailer)) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			/* Ordering is important here, the magazine of a region may potentially change
-			 * during mag_lock_zine_for_region_trailer, so src_mag_index must be taken
-			 * after we've obtained the lock.
-			 */
-			mag_index_t src_mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(tiny);
-
-			/* We can (and must) ignore magazines that are already in the recirc depot. */
-			if (src_mag_index == DEPOT_MAGAZINE_INDEX) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			if (REGION_TRAILER_FOR_TINY_REGION(tiny)->pinned_to_depot > 0) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			if (tiny == mag_ptr->mag_last_region && (mag_ptr->mag_bytes_free_at_end || mag_ptr->mag_bytes_free_at_start)) {
-				tiny_finalize_region(rack, mag_ptr);
-			}
-
-			/* Because this region is currently in use, we can't safely madvise it while
-			 * it's attached to the magazine. For this operation we have to remove it from
-			 * the current mag, attach it to the depot and then madvise.
-			 */
-
-			recirc_list_extract(rack, mag_ptr, REGION_TRAILER_FOR_TINY_REGION(tiny));
-			int objects_in_use = tiny_free_detach_region(rack, mag_ptr, tiny);
-
-			SZONE_MAGAZINE_PTR_LOCK(tiny_depot_ptr);
-			MAGAZINE_INDEX_FOR_TINY_REGION(tiny) = DEPOT_MAGAZINE_INDEX;
-			MALLOC_ASSERT(REGION_TRAILER_FOR_TINY_REGION(tiny)->pinned_to_depot == 0);
-
-			size_t bytes_inplay = tiny_free_reattach_region(rack, tiny_depot_ptr, tiny);
-
-			/* Fix up the metadata of the target magazine while the region is in the depot. */
-			mag_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-			mag_ptr->num_bytes_in_magazine -= TINY_HEAP_SIZE;
-			mag_ptr->mag_num_objects -= objects_in_use;
-
-			/* Now we can drop the magazine lock of the source mag. */
-			SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-
-			tiny_depot_ptr->mag_num_bytes_in_objects += bytes_inplay;
-			tiny_depot_ptr->num_bytes_in_magazine += TINY_HEAP_SIZE;
-			tiny_depot_ptr->mag_num_objects -= objects_in_use;
-
-			recirc_list_splice_last(rack, tiny_depot_ptr, REGION_TRAILER_FOR_TINY_REGION(tiny));
-
-			/* Actually do the scan, done holding the depot lock, the call will drop the lock
-			 * around the actual madvise syscalls.
-			 */
-			tiny_free_scan_madvise_free(rack, tiny_depot_ptr, tiny);
-
-			/* Now the region is in the recirc depot, the next allocations to require more
-			 * blocks will come along and take one of these regions back out of the depot.
-			 * As OS X madvise's reuse on an per-region basis, we leave as many of these
-			 * regions in the depot as possible after memory pressure.
-			 */
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_depot_ptr);
-		}
-	}
-}
-#endif // CONFIG_MADVISE_PRESSURE_RELIEF
 
 static MALLOC_INLINE void
-tiny_madvise_free_range_no_lock(rack_t *rack,
+tiny_madvise_free_range_no_lock(szone_t *szone,
 								magazine_t *tiny_mag_ptr,
 								region_t region,
 								void *headptr,
@@ -1105,159 +651,151 @@
 		uintptr_t free_hi = MIN(trunc_extent, hi);
 
 		if (free_lo < free_hi) {
-			tiny_free_list_remove_ptr(rack, tiny_mag_ptr, ptr, msize);
+			tiny_free_list_remove_ptr(szone, tiny_mag_ptr, ptr, msize);
 			set_tiny_meta_header_in_use(ptr, msize);
 
 			OSAtomicIncrement32Barrier(&(node->pinned_to_depot));
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-			mvm_madvise_free(rack, region, free_lo, free_hi, &rack->last_madvise, rack->debug_flags & MALLOC_DO_SCRIBBLE);
-			SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+			madvise_free_range(szone, region, free_lo, free_hi, &szone->last_tiny_advise);
+			SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
 			OSAtomicDecrement32Barrier(&(node->pinned_to_depot));
 
 			set_tiny_meta_header_free(ptr, msize);
-			tiny_free_list_add_ptr(rack, tiny_mag_ptr, ptr, msize);
-		}
-	}
-}
-
-#if CONFIG_RECIRC_DEPOT
+			tiny_free_list_add_ptr(szone, tiny_mag_ptr, ptr, msize);
+		}
+	}
+}
+
 static boolean_t
-tiny_get_region_from_depot(rack_t *rack, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
-{
-	magazine_t *depot_ptr = &(rack->magazines[DEPOT_MAGAZINE_INDEX]);
+tiny_get_region_from_depot(szone_t *szone, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
+{
+	magazine_t *depot_ptr = &(szone->tiny_magazines[DEPOT_MAGAZINE_INDEX]);
+
+	/* FIXME: Would Uniprocessor benefit from recirc and MADV_FREE? */
+	if (szone->num_tiny_magazines == 1) { // Uniprocessor, single magazine, so no recirculation necessary
+		return 0;
+	}
 
 #if DEBUG_MALLOC
 	if (DEPOT_MAGAZINE_INDEX == mag_index) {
-		malloc_zone_error(rack->debug_flags, true, "tiny_get_region_from_depot called for magazine index -1\n");
+		szone_error(szone, 1, "tiny_get_region_from_depot called for magazine index -1", NULL, NULL);
 		return 0;
 	}
 #endif
 
-	SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
+	SZONE_MAGAZINE_PTR_LOCK(szone, depot_ptr);
 
 	// Appropriate a Depot'd region that can satisfy requested msize.
 	region_trailer_t *node;
 	region_t sparse_region;
-	msize_t try_msize = msize;
 
 	while (1) {
-		sparse_region = tiny_find_msize_region(rack, depot_ptr, DEPOT_MAGAZINE_INDEX, try_msize);
+		sparse_region = tiny_find_msize_region(szone, depot_ptr, DEPOT_MAGAZINE_INDEX, msize);
 		if (NULL == sparse_region) { // Depot empty?
-			SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, depot_ptr);
 			return 0;
 		}
 
 		node = REGION_TRAILER_FOR_TINY_REGION(sparse_region);
-		if (0 == node->pinned_to_depot) {
-			// Found one!
+		if (0 >= node->pinned_to_depot) {
 			break;
 		}
 
-		// Try the next msize up - maybe the head of its free list will be in
-		// a region we can use. Once we get the region we'll still allocate the
-		// original msize.
-		try_msize++;
-
-		if (try_msize > NUM_TINY_SLOTS) {
-			// Tried all the msizes but couldn't get a usable region. Let's
-			// give up for now and we'll allocate a new region from the kernel.
-			SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-			return 0;
-		}
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, depot_ptr);
+		yield();
+		SZONE_MAGAZINE_PTR_LOCK(szone, depot_ptr);
 	}
 
 	// disconnect node from Depot
-	recirc_list_extract(rack, depot_ptr, node);
+	recirc_list_extract(szone, depot_ptr, node);
 
 	// Iterate the region pulling its free entries off the (locked) Depot's free list
-	int objects_in_use = tiny_free_detach_region(rack, depot_ptr, sparse_region);
+	int objects_in_use = tiny_free_detach_region(szone, depot_ptr, sparse_region);
 
 	// Transfer ownership of the region
 	MAGAZINE_INDEX_FOR_TINY_REGION(sparse_region) = mag_index;
-	MALLOC_ASSERT(node->pinned_to_depot == 0);
+	node->pinned_to_depot = 0;
 
 	// Iterate the region putting its free entries on its new (locked) magazine's free list
-	size_t bytes_inplay = tiny_free_reattach_region(rack, tiny_mag_ptr, sparse_region);
+	size_t bytes_inplay = tiny_free_reattach_region(szone, tiny_mag_ptr, sparse_region);
 
 	depot_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-	depot_ptr->num_bytes_in_magazine -= TINY_HEAP_SIZE;
+	depot_ptr->num_bytes_in_magazine -= TINY_REGION_PAYLOAD_BYTES;
 	depot_ptr->mag_num_objects -= objects_in_use;
 
 	tiny_mag_ptr->mag_num_bytes_in_objects += bytes_inplay;
-	tiny_mag_ptr->num_bytes_in_magazine += TINY_HEAP_SIZE;
+	tiny_mag_ptr->num_bytes_in_magazine += TINY_REGION_PAYLOAD_BYTES;
 	tiny_mag_ptr->mag_num_objects += objects_in_use;
 
-	// connect to magazine as last node
-	recirc_list_splice_last(rack, tiny_mag_ptr, node);
-
-	SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-
-	// DTrace USDT Probe
-	MAGMALLOC_DEPOTREGION(TINY_SZONE_FROM_RACK(rack), (int)mag_index, (void *)sparse_region,
-			TINY_REGION_SIZE, (int)BYTES_USED_FOR_TINY_REGION(sparse_region));
+	// connect to magazine as first node
+	recirc_list_splice_first(szone, tiny_mag_ptr, node);
+
+	SZONE_MAGAZINE_PTR_UNLOCK(szone, depot_ptr);
+
+	// madvise() outside the Depot lock
+	(void)madvise_reuse_range(szone, sparse_region, (uintptr_t)sparse_region, (uintptr_t)sparse_region + TINY_REGION_PAYLOAD_BYTES);
+
+	MAGMALLOC_DEPOTREGION((void *)szone, (int)mag_index, (void *)sparse_region, TINY_REGION_SIZE,
+						  (int)BYTES_USED_FOR_TINY_REGION(sparse_region)); // DTrace USDT Probe
 
 	return 1;
 }
 
+#if CONFIG_RECIRC_DEPOT
 static region_t
-tiny_free_try_depot_unmap_no_lock(rack_t *rack, magazine_t *depot_ptr, region_trailer_t *node)
-{
-	if (0 < node->bytes_used || 0 < node->pinned_to_depot ||
-		depot_ptr->recirculation_entries < recirc_retained_regions)
-	{
+tiny_free_try_depot_unmap_no_lock(szone_t *szone, magazine_t *depot_ptr, region_trailer_t *node)
+{
+	if (0 < node->bytes_used || 0 < node->pinned_to_depot || depot_ptr->recirculation_entries < (szone->num_tiny_magazines * 2)) {
 		return NULL;
 	}
 
 	// disconnect node from Depot
-	recirc_list_extract(rack, depot_ptr, node);
+	recirc_list_extract(szone, depot_ptr, node);
 
 	// Iterate the region pulling its free entries off the (locked) Depot's free list
 	region_t sparse_region = TINY_REGION_FOR_PTR(node);
-	int objects_in_use = tiny_free_detach_region(rack, depot_ptr, sparse_region);
+	int objects_in_use = tiny_free_detach_region(szone, depot_ptr, sparse_region);
 
 	if (0 == objects_in_use) {
-		if (!rack_region_remove(rack, sparse_region, node)) {
+		// Invalidate the hash table entry for this region with HASHRING_REGION_DEALLOCATED.
+		// Using HASHRING_REGION_DEALLOCATED preserves the collision chain, using HASHRING_OPEN_ENTRY (0) would not.
+		rgnhdl_t pSlot = hash_lookup_region_no_lock(szone->tiny_region_generation->hashed_regions,
+													szone->tiny_region_generation->num_regions_allocated, szone->tiny_region_generation->num_regions_allocated_shift,
+													sparse_region);
+		if (NULL == pSlot) {
+			szone_error(szone, 1, "tiny_free_try_depot_unmap_no_lock hash lookup failed:", NULL, "%p\n", sparse_region);
 			return NULL;
 		}
-		depot_ptr->num_bytes_in_magazine -= TINY_HEAP_SIZE;
+		*pSlot = HASHRING_REGION_DEALLOCATED;
+		depot_ptr->num_bytes_in_magazine -= TINY_REGION_PAYLOAD_BYTES;
+		__sync_fetch_and_add(&(szone->num_tiny_regions_dealloc), 1); // Atomically increment num_tiny_regions_dealloc
 
 		// Caller will transfer ownership of the region back to the OS with no locks held
-		MAGMALLOC_DEALLOCREGION(TINY_SZONE_FROM_RACK(rack),
-				(void *)sparse_region, TINY_REGION_SIZE); // DTrace USDT Probe
+		MAGMALLOC_DEALLOCREGION((void *)szone, (void *)sparse_region, TINY_REGION_SIZE); // DTrace USDT Probe
 		return sparse_region;
 	} else {
-		malloc_zone_error(rack->debug_flags, true,
-				"tiny_free_try_depot_unmap_no_lock objects_in_use not zero: %d\n",
-				objects_in_use);
+		szone_error(szone, 1, "tiny_free_try_depot_unmap_no_lock objects_in_use not zero:", NULL, "%d\n", objects_in_use);
 		return NULL;
 	}
 }
 
 static boolean_t
-tiny_free_do_recirc_to_depot(rack_t *rack, magazine_t *tiny_mag_ptr, mag_index_t mag_index)
+tiny_free_do_recirc_to_depot(szone_t *szone, magazine_t *tiny_mag_ptr, mag_index_t mag_index)
 {
 	// The entire magazine crossed the "emptiness threshold". Transfer a region
 	// from this magazine to the Depot. Choose a region that itself has crossed the emptiness threshold (i.e
 	// is at least fraction "f" empty.) Such a region will be marked "suitable" on the recirculation list.
-	// Start from the last node in order to keep the regions created earlier at the front of the list for
-	// as long as possible. This helps reduce fragmentation.
-	region_trailer_t *node = tiny_mag_ptr->lastNode;
-
-	while (node && (!node->recirc_suitable || node->pinned_to_depot)) {
-		// If we skip a node due to pinned_to_depot being non-zero, it must be
-		// because another thread is madvising the same region in
-		// tiny_madvise_free_range_no_lock(), called from tiny_free_no_lock().
-		// When that's done, the same thread will enter tiny_free_try_recirc_to_depot()
-		// for the same region, which will come back here. So this just defers
-		// recirculation of the region.
-		node = node->prev;
-	}
-
-	if (!node) {
-#if DEBUG_MALLOC
-		malloc_report(ASL_LEVEL_INFO, "*** tiny_free_do_recirc_to_depot end of list\n");
-#endif
-		return TRUE; // Caller must SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+	region_trailer_t *node = tiny_mag_ptr->firstNode;
+
+	while (node && !node->recirc_suitable) {
+		node = node->next;
+	}
+
+	if (NULL == node) {
+#if DEBUG_MALLOC
+		malloc_printf("*** tiny_free_do_recirc_to_depot end of list\n");
+#endif
+		return TRUE; // Caller must SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 	}
 
 	region_t sparse_region = TINY_REGION_FOR_PTR(node);
@@ -1265,62 +803,58 @@
 	// Deal with unclaimed memory -- mag_bytes_free_at_end or mag_bytes_free_at_start
 	if (sparse_region == tiny_mag_ptr->mag_last_region &&
 		(tiny_mag_ptr->mag_bytes_free_at_end || tiny_mag_ptr->mag_bytes_free_at_start)) {
-		tiny_finalize_region(rack, tiny_mag_ptr);
+		tiny_finalize_region(szone, tiny_mag_ptr);
 	}
 
 	// disconnect "suitable" node from magazine
-	recirc_list_extract(rack, tiny_mag_ptr, node);
+	recirc_list_extract(szone, tiny_mag_ptr, node);
 
 	// Iterate the region pulling its free entries off its (locked) magazine's free list
-	int objects_in_use = tiny_free_detach_region(rack, tiny_mag_ptr, sparse_region);
-	magazine_t *depot_ptr = &(rack->magazines[DEPOT_MAGAZINE_INDEX]);
+	int objects_in_use = tiny_free_detach_region(szone, tiny_mag_ptr, sparse_region);
+	magazine_t *depot_ptr = &(szone->tiny_magazines[DEPOT_MAGAZINE_INDEX]);
 
 	// hand over the region to the (locked) Depot
-	SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
+	SZONE_MAGAZINE_PTR_LOCK(szone, depot_ptr);
 	// this will cause tiny_free_list_add_ptr called by tiny_free_reattach_region to use
 	// the depot as its target magazine, rather than magazine formerly associated with sparse_region
 	MAGAZINE_INDEX_FOR_TINY_REGION(sparse_region) = DEPOT_MAGAZINE_INDEX;
 	node->pinned_to_depot = 0;
 
 	// Iterate the region putting its free entries on Depot's free list
-	size_t bytes_inplay = tiny_free_reattach_region(rack, depot_ptr, sparse_region);
+	size_t bytes_inplay = tiny_free_reattach_region(szone, depot_ptr, sparse_region);
 
 	tiny_mag_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-	tiny_mag_ptr->num_bytes_in_magazine -= TINY_HEAP_SIZE;
+	tiny_mag_ptr->num_bytes_in_magazine -= TINY_REGION_PAYLOAD_BYTES;
 	tiny_mag_ptr->mag_num_objects -= objects_in_use;
 
-	SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr); // Unlock the originating magazine
+	SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr); // Unlock the originating magazine
 
 	depot_ptr->mag_num_bytes_in_objects += bytes_inplay;
-	depot_ptr->num_bytes_in_magazine += TINY_HEAP_SIZE;
+	depot_ptr->num_bytes_in_magazine += TINY_REGION_PAYLOAD_BYTES;
 	depot_ptr->mag_num_objects += objects_in_use;
 
 	// connect to Depot as last node
-	recirc_list_splice_last(rack, depot_ptr, node);
-
-	MAGMALLOC_RECIRCREGION(TINY_SZONE_FROM_RACK(rack), (int)mag_index, (void *)sparse_region, TINY_REGION_SIZE,
+	recirc_list_splice_last(szone, depot_ptr, node);
+
+	MAGMALLOC_RECIRCREGION((void *)szone, (int)mag_index, (void *)sparse_region, TINY_REGION_SIZE,
 						   (int)BYTES_USED_FOR_TINY_REGION(sparse_region)); // DTrace USDT Probe
 
-#if CONFIG_AGGRESSIVE_MADVISE
-	if (!aggressive_madvise_enabled)
-#endif
-	{
-		// Mark free'd dirty pages with MADV_FREE to reduce memory pressure
-		tiny_free_scan_madvise_free(rack, depot_ptr, sparse_region);
-	}
+#if !CONFIG_AGGRESSIVE_MADVISE
+	// Mark free'd dirty pages with MADV_FREE to reduce memory pressure
+	tiny_free_scan_madvise_free(szone, depot_ptr, sparse_region);
+#endif
 
 	// If the region is entirely empty vm_deallocate() it outside the depot lock
-	region_t r_dealloc = tiny_free_try_depot_unmap_no_lock(rack, depot_ptr, node);
-	SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
+	region_t r_dealloc = tiny_free_try_depot_unmap_no_lock(szone, depot_ptr, node);
+	SZONE_MAGAZINE_PTR_UNLOCK(szone, depot_ptr);
 	if (r_dealloc) {
-		mvm_deallocate_pages(r_dealloc, TINY_REGION_SIZE,
-				MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags));
+		deallocate_pages(szone, r_dealloc, TINY_REGION_SIZE, 0);
 	}
 	return FALSE; // Caller need not unlock the originating magazine
 }
 
 static MALLOC_INLINE boolean_t
-tiny_free_try_recirc_to_depot(rack_t *rack,
+tiny_free_try_recirc_to_depot(szone_t *szone,
 							  magazine_t *tiny_mag_ptr,
 							  mag_index_t mag_index,
 							  region_t region,
@@ -1332,9 +866,13 @@
 	region_trailer_t *node = REGION_TRAILER_FOR_TINY_REGION(region);
 	size_t bytes_used = node->bytes_used;
 
-	if (DEPOT_MAGAZINE_INDEX != mag_index) {
+	/* FIXME: Would Uniprocessor benefit from recirc and MADV_FREE? */
+	if (szone->num_tiny_magazines == 1) { // Uniprocessor, single magazine, so no recirculation necessary
+		/* NOTHING */
+		return TRUE; // Caller must do SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr)
+	} else if (DEPOT_MAGAZINE_INDEX != mag_index) {
 		// Emptiness discriminant
-		if (tiny_region_below_recirc_threshold(region)) {
+		if (bytes_used < DENSITY_THRESHOLD(TINY_REGION_PAYLOAD_BYTES)) {
 			/* Region has crossed threshold from density to sparsity. Mark it "suitable" on the
 			 * recirculation candidates list. */
 			node->recirc_suitable = TRUE;
@@ -1346,18 +884,18 @@
 		// Has the entire magazine crossed the "emptiness threshold"? If so, transfer a region
 		// from this magazine to the Depot. Choose a region that itself has crossed the emptiness threshold (i.e
 		// is at least fraction "f" empty.) Such a region will be marked "suitable" on the recirculation list.
-		if (tiny_magazine_below_recirc_threshold(tiny_mag_ptr)) {
-			return tiny_free_do_recirc_to_depot(rack, tiny_mag_ptr, mag_index);
+		size_t a = tiny_mag_ptr->num_bytes_in_magazine;	// Total bytes allocated to this magazine
+		size_t u = tiny_mag_ptr->mag_num_bytes_in_objects; // In use (malloc'd) from this magaqzine
+
+		if (a - u > ((3 * TINY_REGION_PAYLOAD_BYTES) / 2) && u < DENSITY_THRESHOLD(a)) {
+			return tiny_free_do_recirc_to_depot(szone, tiny_mag_ptr, mag_index);
 		}
 	} else {
-#if CONFIG_AGGRESSIVE_MADVISE
-		if (!aggressive_madvise_enabled)
-#endif
-		{
-			// We are free'ing into the depot, so madvise as we do so unless we were madvising every incoming
-			// allocation anyway.
-			tiny_madvise_free_range_no_lock(rack, tiny_mag_ptr, region, headptr, headsize, ptr, msize);
-		}
+#if !CONFIG_AGGRESSIVE_MADVISE
+		// We are free'ing into the depot, so madvise as we do so unless we were madvising every incoming
+		// allocation anyway.
+		tiny_madvise_free_range_no_lock(szone, tiny_mag_ptr, region, headptr, headsize, ptr, msize);
+#endif
 
 		if (0 < bytes_used || 0 < node->pinned_to_depot) {
 			/* Depot'd region is still live. Leave it in place on the Depot's recirculation list
@@ -1365,25 +903,20 @@
 			 * with detach_region/reattach_region */
 		} else {
 			/* Depot'd region is just now empty. Consider return to OS. */
-			region_t r_dealloc = tiny_free_try_depot_unmap_no_lock(rack, tiny_mag_ptr, node);
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			region_t r_dealloc = tiny_free_try_depot_unmap_no_lock(szone, tiny_mag_ptr, node);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 			if (r_dealloc) {
-				mvm_deallocate_pages(r_dealloc, TINY_REGION_SIZE,
-						MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags));
+				deallocate_pages(szone, r_dealloc, TINY_REGION_SIZE, 0);
 			}
 			return FALSE; // Caller need not unlock
 		}
 	}
-	return TRUE; // Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr)
+	return TRUE; // Caller must do SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr)
 }
 #endif // CONFIG_RECIRC_DEPOT
 
-#define TINY_FREE_FLAG_PARTIAL 0x1
-#define TINY_FREE_FLAG_FROM_CACHE 0x2
-
 boolean_t
-tiny_free_no_lock(rack_t *rack, magazine_t *tiny_mag_ptr, mag_index_t mag_index,
-		region_t region, void *ptr, msize_t msize, uint32_t flags)
+tiny_free_no_lock(szone_t *szone, magazine_t *tiny_mag_ptr, mag_index_t mag_index, region_t region, void *ptr, msize_t msize)
 {
 	void *original_ptr = ptr;
 	size_t original_size = TINY_BYTES_FOR_MSIZE(msize);
@@ -1396,67 +929,57 @@
 
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in tiny_free_no_lock(), ptr=%p, msize=%d\n", ptr, msize);
+		malloc_printf("in tiny_free_no_lock(), ptr=%p, msize=%d\n", ptr, msize);
 	}
 	if (!msize) {
-		malloc_zone_error(rack->debug_flags, true,
-				"trying to free tiny block that is too small in tiny_free_no_lock(), ptr=%p, msize=%d\n",
-				ptr, msize);
-	}
-#endif
-
-	// Check that the region cookie is intact.
-	region_check_cookie(region, &REGION_COOKIE_FOR_TINY_REGION(region));
+		szone_error(szone, 1, "trying to free tiny block that is too small", ptr, "in tiny_free_no_lock(), ptr=%p, msize=%d\n", ptr,
+					msize);
+	}
+#endif
 
 	// We try to coalesce this block with the preceeding one
 	previous = tiny_previous_preceding_free(ptr, &previous_msize);
 	if (previous) {
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr) || LOG(szone, previous)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_free_no_lock(), coalesced backwards for %p previous=%p\n", ptr, previous);
+			malloc_printf("in tiny_free_no_lock(), coalesced backwards for %p previous=%p\n", ptr, previous);
 		}
 #endif
 
 		// clear the meta_header since this is no longer the start of a block
 		set_tiny_meta_header_middle(ptr);
-		tiny_free_list_remove_ptr(rack, tiny_mag_ptr, previous, previous_msize);
-
-		// zero out the trailing inline msize of the block to connect the zero
-		// prefix of this block to the newly free block
-		zero_tiny_free_inline_meta_following(previous, previous_msize);
-
+		tiny_free_list_remove_ptr(szone, tiny_mag_ptr, previous, previous_msize);
 		ptr = previous;
 		msize += previous_msize;
 	}
-
 	// We try to coalesce with the next block
-	if ((next_block < TINY_REGION_HEAP_END(region)) && tiny_meta_header_is_free(next_block)) {
+	if ((next_block < TINY_REGION_END(region)) && tiny_meta_header_is_free(next_block)) {
 		next_msize = get_tiny_free_size(next_block);
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr) || LOG(szone, next_block)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_free_no_lock(), for ptr=%p, msize=%d coalesced forward=%p next_msize=%d\n", ptr, msize,
+			malloc_printf("in tiny_free_no_lock(), for ptr=%p, msize=%d coalesced forward=%p next_msize=%d\n", ptr, msize,
 						  next_block, next_msize);
 		}
 #endif
 		// If we are coalescing with the next block, and the next block is in
 		// the last slot of the free list, then we optimize this case here to
-		// avoid removing next_block from the slot NUM_TINY_SLOTS and then adding ptr back
-		// to slot NUM_TINY_SLOTS.
-		if (next_msize > NUM_TINY_SLOTS) {
+		// avoid removing next_block from the slot (NUM_TINY_SLOTS - 1) and then adding ptr back
+		// to slot (NUM_TINY_SLOTS - 1).
+		if (next_msize >= NUM_TINY_SLOTS) {
 			msize += next_msize;
 
 			big_free_block = (tiny_free_list_t *)next_block;
-			after_next_block = free_list_unchecksum_ptr(rack, &big_free_block->next);
-			before_next_block = free_list_unchecksum_ptr(rack, &big_free_block->previous);
+			after_next_block = free_list_unchecksum_ptr(szone, &big_free_block->next);
+			before_next_block = free_list_unchecksum_ptr(szone, &big_free_block->previous);
 
 			if (!before_next_block) {
-				tiny_mag_ptr->mag_free_list[NUM_TINY_SLOTS].p = ptr;
+				tiny_mag_ptr->mag_free_list[NUM_TINY_SLOTS - 1].p = ptr;
 			} else {
-				before_next_block->next.u = free_list_checksum_ptr(rack, ptr);
+				before_next_block->next.u = free_list_checksum_ptr(szone, ptr);
 			}
 
 			if (after_next_block) {
-				after_next_block->previous.u = free_list_checksum_ptr(rack, ptr);
+				after_next_block->previous.u = free_list_checksum_ptr(szone, ptr);
 			}
 
 			// we don't need to checksum these since they are already checksummed
@@ -1465,85 +988,53 @@
 
 			// clear the meta_header to enable coalescing backwards
 			set_tiny_meta_header_middle(big_free_block);
-
-			// zero out inline metadata to continue the zero prefix of the
-			// previous block - must happen before set_tiny_meta_header_free()
-			// reinitializes the new inline metadata
-			zero_tiny_free_inline_meta(big_free_block, next_msize);
-
 			set_tiny_meta_header_free(ptr, msize);
 
-			uint16_t next_block_index = TINY_INDEX_FOR_PTR(big_free_block) + 1;
-			uint16_t ptr_index = TINY_INDEX_FOR_PTR(ptr) + 1;
-			const grain_t slot = NUM_TINY_SLOTS;
-			region_free_blocks_t *free_blocks = &((tiny_region_t)region)->free_blocks_by_slot[slot];
-			if (free_blocks->first_block == next_block_index) {
-				free_blocks->first_block = ptr_index;
-			}
-			if (free_blocks->last_block == next_block_index) {
-				free_blocks->last_block = ptr_index;
-			}
 			goto tiny_free_ending;
 		}
-		tiny_free_list_remove_ptr(rack, tiny_mag_ptr, next_block, next_msize);
+		tiny_free_list_remove_ptr(szone, tiny_mag_ptr, next_block, next_msize);
 		set_tiny_meta_header_middle(next_block); // clear the meta_header to enable coalescing backwards
-		// zero out inline metadata to continue the zero prefix of the previous
-		// block
-		zero_tiny_free_inline_meta(next_block, next_msize);
 		msize += next_msize;
 	}
 
-	if (malloc_zero_policy != MALLOC_ZERO_ON_FREE) {
-		// The tiny cache already scribbles free blocks as they go through the
-		// cache, so we do not need to do it here.
-		//
-		// XXX This should probably also be conditional on CONFIG_TINY_CACHE
-		if ((rack->debug_flags & MALLOC_DO_SCRIBBLE) &&
-				!(flags & TINY_FREE_FLAG_FROM_CACHE)) {
-			memset(ptr, SCRABBLE_BYTE, TINY_BYTES_FOR_MSIZE(msize));
-		}
-	}
-
-	tiny_free_list_add_ptr(rack, tiny_mag_ptr, ptr, msize);
+	// The tiny cache already scribbles free blocks as they go through the
+	// cache whenever msize < TINY_QUANTUM , so we do not need to do it here.
+	if ((szone->debug_flags & MALLOC_DO_SCRIBBLE) && msize && (msize >= TINY_QUANTUM)) {
+		memset(ptr, SCRABBLE_BYTE, TINY_BYTES_FOR_MSIZE(msize));
+	}
+
+	tiny_free_list_add_ptr(szone, tiny_mag_ptr, ptr, msize);
 
 tiny_free_ending:
+
+	tiny_mag_ptr->mag_num_objects--;
 	// we use original_size and not msize to avoid double counting the coalesced blocks
 	tiny_mag_ptr->mag_num_bytes_in_objects -= original_size;
 
 	// Update this region's bytes in use count
-	region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(region);
-	size_t bytes_used = trailer->bytes_used - original_size;
-	trailer->bytes_used = (unsigned int)bytes_used;
-
-	// Partial free accounts for the case where we allocate a block for
-	// posix_memalign and then free some range of bytes at the start and/or
-	// the end. In that case, we aren't changing the number of allocated objects.
-	// Similarly for realloc() in the case where we shrink in place.
-	if (!(flags & TINY_FREE_FLAG_PARTIAL)) {
-		trailer->objects_in_use--;
-		tiny_mag_ptr->mag_num_objects--;
-	}
+	region_trailer_t *node = REGION_TRAILER_FOR_TINY_REGION(region);
+	size_t bytes_used = node->bytes_used - original_size;
+	node->bytes_used = (unsigned int)bytes_used;
+
 #if CONFIG_AGGRESSIVE_MADVISE
-	if (aggressive_madvise_enabled) {
-		// Platforms that want to madvise every freed allocation do so here, even if we continue
-		// on to use the recirc depot after.
-		tiny_madvise_free_range_no_lock(rack, tiny_mag_ptr, region, original_ptr, original_size, ptr, msize);
-	}
-#endif
-
-	// Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr) if this function
+	// Platforms that want to madvise every freed allocation do so here, even if we continue
+	// on to use the recirc depot after.
+	tiny_madvise_free_range_no_lock(szone, tiny_mag_ptr, region, original_ptr, original_size, ptr, msize);
+#endif
+
+	// Caller must do SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr) if this function
 	// returns TRUE.
 	boolean_t needs_unlock = TRUE;
 
 #if CONFIG_RECIRC_DEPOT
-	needs_unlock = tiny_free_try_recirc_to_depot(rack, tiny_mag_ptr, mag_index, region, original_ptr, original_size, ptr, msize);
-#endif // CONFIG_RECIRC_DEPOT
+	needs_unlock = tiny_free_try_recirc_to_depot(szone, tiny_mag_ptr, mag_index, region, original_ptr, original_size, ptr, msize);
+#endif
 	return needs_unlock;
 }
 
 // Allocates from the last region or a freshly allocated region
 static void *
-tiny_malloc_from_region_no_lock(rack_t *rack,
+tiny_malloc_from_region_no_lock(szone_t *szone,
 								magazine_t *tiny_mag_ptr,
 								mag_index_t mag_index,
 								msize_t msize,
@@ -1553,32 +1044,59 @@
 
 	// Deal with unclaimed memory -- mag_bytes_free_at_end or mag_bytes_free_at_start
 	if (tiny_mag_ptr->mag_bytes_free_at_end || tiny_mag_ptr->mag_bytes_free_at_start) {
-		tiny_finalize_region(rack, tiny_mag_ptr);
-	}
-
-	tiny_region_t region = (tiny_region_t)aligned_address;
+		tiny_finalize_region(szone, tiny_mag_ptr);
+	}
 
 	// We set the unused bits of the header in the last pair to be all ones, and those of the inuse to zeroes.
-#if NUM_TINY_BLOCKS & 31
-	const uint32_t header = 0xFFFFFFFFU << (NUM_TINY_BLOCKS & 31);
-#else
-	const uint32_t header = 0;
-#endif
-	region->pairs[CEIL_NUM_TINY_BLOCKS_WORDS - 1].header = header;
-	region->pairs[CEIL_NUM_TINY_BLOCKS_WORDS - 1].inuse = 0;
-
+	((tiny_region_t)aligned_address)->pairs[CEIL_NUM_TINY_BLOCKS_WORDS - 1].header =
+	(NUM_TINY_BLOCKS & 31) ? (0xFFFFFFFFU << (NUM_TINY_BLOCKS & 31)) : 0;
+	((tiny_region_t)aligned_address)->pairs[CEIL_NUM_TINY_BLOCKS_WORDS - 1].inuse = 0;
+
+	// Here find the only place in tinyland that (infrequently) takes the tiny_regions_lock.
+	// Only one thread at a time should be permitted to assess the density of the hash
+	// ring and adjust if needed.
+	// Only one thread at a time should be permitted to insert its new region on
+	// the hash ring.
+	// It is safe for all other threads to read the hash ring (hashed_regions) and
+	// the associated sizes (num_regions_allocated and num_tiny_regions).
+
+	_malloc_lock_lock(&szone->tiny_regions_lock);
+
+	// Check to see if the hash ring of tiny regions needs to grow.  Try to
+	// avoid the hash ring becoming too dense.
+	if (szone->tiny_region_generation->num_regions_allocated < (2 * szone->num_tiny_regions)) {
+		region_t *new_regions;
+		size_t new_size;
+		size_t new_shift = szone->tiny_region_generation->num_regions_allocated_shift; // In/Out parameter
+		new_regions = hash_regions_grow_no_lock(szone, szone->tiny_region_generation->hashed_regions,
+												szone->tiny_region_generation->num_regions_allocated, &new_shift, &new_size);
+		// Do not deallocate the current hashed_regions allocation since someone may
+		// be iterating it.  Instead, just leak it.
+
+		// Prepare to advance to the "next generation" of the hash ring.
+		szone->tiny_region_generation->nextgen->hashed_regions = new_regions;
+		szone->tiny_region_generation->nextgen->num_regions_allocated = new_size;
+		szone->tiny_region_generation->nextgen->num_regions_allocated_shift = new_shift;
+
+		// Throw the switch to atomically advance to the next generation.
+		szone->tiny_region_generation = szone->tiny_region_generation->nextgen;
+		// Ensure everyone sees the advance.
+		OSMemoryBarrier();
+	}
 	// Tag the region at "aligned_address" as belonging to us,
 	// and so put it under the protection of the magazine lock we are holding.
 	// Do this before advertising "aligned_address" on the hash ring(!)
-	MAGAZINE_INDEX_FOR_TINY_REGION(region) = mag_index;
-
-	// Insert the new region into the hash ring
-	rack_region_insert(rack, region);
-
-	tiny_mag_ptr->mag_last_region = region;
-	BYTES_USED_FOR_TINY_REGION(region) = TINY_BYTES_FOR_MSIZE(msize);
-	OBJECTS_IN_USE_FOR_TINY_REGION(region) = 1;
-
+	MAGAZINE_INDEX_FOR_TINY_REGION(aligned_address) = mag_index;
+
+	// Insert the new region into the hash ring, and update malloc statistics
+	hash_region_insert_no_lock(szone->tiny_region_generation->hashed_regions, szone->tiny_region_generation->num_regions_allocated,
+							   szone->tiny_region_generation->num_regions_allocated_shift, aligned_address);
+
+	szone->num_tiny_regions++;
+	_malloc_lock_unlock(&szone->tiny_regions_lock);
+
+	tiny_mag_ptr->mag_last_region = aligned_address;
+	BYTES_USED_FOR_TINY_REGION(aligned_address) = TINY_BYTES_FOR_MSIZE(msize);
 #if CONFIG_ASLR_INTERNAL
 	int offset_msize = malloc_entropy[0] & TINY_ENTROPY_MASK;
 #if DEBUG_MALLOC
@@ -1586,17 +1104,17 @@
 		offset_msize = strtol(getenv("MallocASLRForce"), NULL, 0) & TINY_ENTROPY_MASK;
 	}
 	if (getenv("MallocASLRPrint")) {
-		malloc_report(ASL_LEVEL_INFO, "Region: %p offset: %d\n", region, offset_msize);
+		malloc_printf("Region: %p offset: %d\n", aligned_address, offset_msize);
 	}
 #endif
 #else
 	int offset_msize = 0;
 #endif
-	ptr = (void *)(TINY_REGION_HEAP_BASE(region) + TINY_BYTES_FOR_MSIZE(offset_msize));
+	ptr = (void *)((uintptr_t)aligned_address + TINY_BYTES_FOR_MSIZE(offset_msize));
 	set_tiny_meta_header_in_use(ptr, msize);
 	tiny_mag_ptr->mag_num_objects++;
 	tiny_mag_ptr->mag_num_bytes_in_objects += TINY_BYTES_FOR_MSIZE(msize);
-	tiny_mag_ptr->num_bytes_in_magazine += TINY_HEAP_SIZE;
+	tiny_mag_ptr->num_bytes_in_magazine += TINY_REGION_PAYLOAD_BYTES;
 
 	// We put a header on the last block so that it appears in use (for coalescing, etc...)
 	set_tiny_meta_header_in_use_1((void *)((uintptr_t)ptr + TINY_BYTES_FOR_MSIZE(msize)));
@@ -1613,11 +1131,11 @@
 #endif
 
 	// connect to magazine as last node
-	recirc_list_splice_last(rack, tiny_mag_ptr, REGION_TRAILER_FOR_TINY_REGION(region));
+	recirc_list_splice_last(szone, tiny_mag_ptr, REGION_TRAILER_FOR_TINY_REGION(aligned_address));
 
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_region_no_lock(), ptr=%p, msize=%d\n", ptr, msize);
+		malloc_printf("in tiny_malloc_from_region_no_lock(), ptr=%p, msize=%d\n", ptr, msize);
 	}
 #endif
 	return ptr;
@@ -1627,7 +1145,7 @@
 tiny_memalign(szone_t *szone, size_t alignment, size_t size, size_t span)
 {
 	msize_t mspan = TINY_MSIZE_FOR_BYTES(span + TINY_QUANTUM - 1);
-	void *p = tiny_malloc_should_clear(&szone->tiny_rack, mspan, 0);
+	void *p = szone_malloc(szone, span); // avoids inlining tiny_malloc_should_clear(szone, mspan, 0);
 
 	if (NULL == p) {
 		return NULL;
@@ -1644,9 +1162,8 @@
 		void *q = (void *)(((uintptr_t)p) + pad);
 
 		// Mark q as a block header and in-use, thus creating two blocks.
-		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone->tiny_rack.magazines,
-				REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)),
-				MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)));
+		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone, szone->tiny_magazines,
+																	REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)), MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)));
 		set_tiny_meta_header_in_use(q, msize);
 		tiny_mag_ptr->mag_num_objects++;
 
@@ -1655,10 +1172,11 @@
 		if (mwaste > 0) {
 			BITARRAY_SET(TINY_INUSE_FOR_HEADER(TINY_BLOCK_HEADER_FOR_PTR(q)), TINY_INDEX_FOR_PTR(q) + msize);
 		}
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 
 		// Give up mpad blocks beginning at p to the tiny free list
-		free_tiny(&szone->tiny_rack, p, TINY_REGION_FOR_PTR(p), TINY_BYTES_FOR_MSIZE(mpad), true);
+		// region_t r = TINY_REGION_FOR_PTR(p);
+		szone_free(szone, p); // avoids inlining free_tiny(szone, p, &r);
 
 		p = q; // advance p to the desired alignment
 	}
@@ -1666,52 +1184,43 @@
 	if (mwaste > 0) {
 		void *q = (void *)(((uintptr_t)p) + TINY_BYTES_FOR_MSIZE(msize));
 		// Mark q as block header and in-use, thus creating two blocks.
-		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone->tiny_rack.magazines,
-				REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)),
-				MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)));
+		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone, szone->tiny_magazines,
+																	REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)), MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(p)));
 		set_tiny_meta_header_in_use(q, mwaste);
 		tiny_mag_ptr->mag_num_objects++;
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 
 		// Give up mwaste blocks beginning at q to the tiny free list
-		free_tiny(&szone->tiny_rack, q, TINY_REGION_FOR_PTR(q), TINY_BYTES_FOR_MSIZE(mwaste), true);
+		// region_t r = TINY_REGION_FOR_PTR(q);
+		szone_free(szone, q); // avoids inlining free_tiny(szone, q, &r);
 	}
 
 	return p; // p has the desired size and alignment, and can later be free()'d
 }
 
-boolean_t
-tiny_claimed_address(rack_t *rack, void *ptr)
-{
-	region_t r = tiny_region_for_ptr_no_lock(rack, ptr);
-	return r && ptr >= TINY_REGION_HEAP_BASE(r)
-			&& ptr < TINY_REGION_HEAP_END(r);
-}
-
 void *
-tiny_try_shrink_in_place(rack_t *rack, void *ptr, size_t old_size, size_t new_good_size)
+tiny_try_shrink_in_place(szone_t *szone, void *ptr, size_t old_size, size_t new_good_size)
 {
 	msize_t new_msize = TINY_MSIZE_FOR_BYTES(new_good_size);
 	msize_t mshrinkage = TINY_MSIZE_FOR_BYTES(old_size) - new_msize;
 
 	if (mshrinkage) {
 		void *q = (void *)((uintptr_t)ptr + TINY_BYTES_FOR_MSIZE(new_msize));
-		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-				REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)),
-				MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)));
+		magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone, szone->tiny_magazines,
+																	REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)), MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)));
 
 		// Mark q as block header and in-use, thus creating two blocks.
 		set_tiny_meta_header_in_use(q, mshrinkage);
 		tiny_mag_ptr->mag_num_objects++;
 
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-		free_tiny(rack, q, TINY_REGION_FOR_PTR(q), 0, true);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+		szone_free(szone, q); // avoid inlining free_tiny(szone, q, ...);
 	}
 	return ptr;
 }
 
 boolean_t
-tiny_try_realloc_in_place(rack_t *rack, void *ptr, size_t old_size, size_t new_size)
+tiny_try_realloc_in_place(szone_t *szone, void *ptr, size_t old_size, size_t new_size)
 {
 	// returns 1 on success
 	msize_t index;
@@ -1719,13 +1228,11 @@
 	unsigned next_index;
 	void *next_block;
 	boolean_t is_free;
-	msize_t next_msize, coalesced_msize, leftover_msize, new_msize;
+	msize_t next_msize, coalesced_msize, leftover_msize;
 	void *leftover;
-	region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr));
 
 	index = TINY_INDEX_FOR_PTR(ptr);
 	old_msize = TINY_MSIZE_FOR_BYTES(old_size);
-	new_msize = TINY_MSIZE_FOR_BYTES(new_size + TINY_QUANTUM - 1);
 	next_index = index + old_msize;
 
 	if (next_index >= NUM_TINY_BLOCKS) {
@@ -1733,106 +1240,46 @@
 	}
 	next_block = (char *)ptr + old_size;
 
-	magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-			trailer,
-			MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)));
+	magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone, szone->tiny_magazines,
+																REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)), MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr)));
 
 	if (DEPOT_MAGAZINE_INDEX == MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr))) {
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 		return 0;
 	}
 
-	coalesced_msize = new_msize - old_msize;
-#if CONFIG_TINY_CACHE
-	void *last_free_ptr = tiny_mag_ptr->mag_last_free;
-	msize_t last_free_msize = tiny_mag_ptr->mag_last_free_msize;
-	if (last_free_ptr == next_block && old_msize + last_free_msize >= new_msize) {
-		/*
-		 * There is a block in mag_last_free and it's immediately after
-		 * this block and it's large enough. We can use some or all of it.
-		 */
-		leftover_msize = last_free_msize - coalesced_msize;
-		if (leftover_msize) {
-			tiny_mag_ptr->mag_last_free_msize -= coalesced_msize;
-			tiny_mag_ptr->mag_last_free += new_size - old_size;
-			// The block in mag_last_free is still marked as header and in-use, so copy that
-			// state to the block that remains. The state for the block that we're going to
-			// use is adjusted by the set_tiny_meta_header_middle() call below.
-			void *leftover_ptr = ((char *)next_block) + TINY_BYTES_FOR_MSIZE(coalesced_msize);
-			set_tiny_meta_header_in_use(leftover_ptr, leftover_msize);
-		} else {
-			// Using the whole block.
-			tiny_mag_ptr->mag_last_free = NULL;
-			tiny_mag_ptr->mag_last_free_msize = 0;
-			tiny_mag_ptr->mag_last_free_rgn = NULL;
-			trailer->objects_in_use--;
-		}
-		set_tiny_meta_header_middle(next_block);
-		tiny_check_zero_or_clear(last_free_ptr, coalesced_msize, false);
-		coalesced_msize = 0; // No net change in memory use
-	} else {
-#endif // CONFIG_TINY_CACHE
-		/*
-		 * Try to expand into unused space immediately after this block.
-		 */
-		msize_t unused_msize = TINY_MSIZE_FOR_BYTES(tiny_mag_ptr->mag_bytes_free_at_end);
-		void *unused_start = TINY_REGION_HEAP_END(TINY_REGION_FOR_PTR(ptr)) - tiny_mag_ptr->mag_bytes_free_at_end;
-		if (tiny_mag_ptr->mag_last_region == TINY_REGION_FOR_PTR(ptr)
-				&& coalesced_msize < unused_msize && unused_start == ptr + old_size) {
-			// The block at the start of mag_bytes_free_at_end is marked as
-			// header/in-use and the next one has header/free. We need to
-			// reset both the header and in-use bit in the first block and we
-			// need to reset the header bit in the second block if it's part of
-			// the new allocation.
-			set_tiny_meta_header_middle(unused_start);
-			if (coalesced_msize > 1) {
-				set_tiny_meta_header_middle(unused_start + TINY_QUANTUM);
-			}
-			tiny_mag_ptr->mag_bytes_free_at_end -= TINY_BYTES_FOR_MSIZE(coalesced_msize);
-			if (tiny_mag_ptr->mag_bytes_free_at_end) {
-				// Mark the first block of the remaining free area as a header and in-use.
-				set_tiny_meta_header_in_use_1(ptr + TINY_BYTES_FOR_MSIZE(new_msize));
-			}
-			tiny_check_zero_or_clear(unused_start, coalesced_msize, false);
-		} else {
-			/*
-			 * Look for a free block immediately afterwards.  If it's large
-			 * enough, we can consume (part of) it.
-			 */
-			is_free = tiny_meta_header_is_free(next_block);
-			if (!is_free) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-				return 0; // next_block is in use;
-			}
-			next_msize = get_tiny_free_size(next_block);
-			if (old_msize + next_msize < new_msize) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-				return 0; // even with next block, not enough
-			}
-			/*
-		 	 * The following block is big enough; pull it from its freelist and chop off enough to satisfy
-		 	 * our needs.
-		 	 */
-			tiny_free_list_remove_ptr(rack, tiny_mag_ptr, next_block, next_msize);
-			set_tiny_meta_header_middle(next_block); // clear the meta_header to enable coalescing backwards
-
-			tiny_check_and_zero_inline_meta_from_freelist(rack, next_block, next_msize);
-			tiny_check_zero_or_clear(next_block, coalesced_msize, false);
-
-			leftover_msize = next_msize - coalesced_msize;
-			if (leftover_msize) {
-				/* there's some left, so put the remainder back */
-				leftover = (void *)((uintptr_t)next_block + TINY_BYTES_FOR_MSIZE(coalesced_msize));
-				tiny_free_list_add_ptr(rack, tiny_mag_ptr, leftover, leftover_msize);
-			}
-			set_tiny_meta_header_in_use(ptr, old_msize + coalesced_msize);
-		}
-#if CONFIG_TINY_CACHE
-	}
-#endif // CONFIG_TINY_CACHE
+	/*
+	 * Look for a free block immediately afterwards.  If it's large enough, we can consume (part of)
+	 * it.
+	 */
+	is_free = tiny_meta_header_is_free(next_block);
+	if (!is_free) {
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+		return 0; // next_block is in use;
+	}
+	next_msize = get_tiny_free_size(next_block);
+	if (old_size + TINY_BYTES_FOR_MSIZE(next_msize) < new_size) {
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+		return 0; // even with next block, not enough
+	}
+	/*
+	 * The following block is big enough; pull it from its freelist and chop off enough to satisfy
+	 * our needs.
+	 */
+	tiny_free_list_remove_ptr(szone, tiny_mag_ptr, next_block, next_msize);
+	set_tiny_meta_header_middle(next_block); // clear the meta_header to enable coalescing backwards
+	coalesced_msize = TINY_MSIZE_FOR_BYTES(new_size - old_size + TINY_QUANTUM - 1);
+	leftover_msize = next_msize - coalesced_msize;
+	if (leftover_msize) {
+		/* there's some left, so put the remainder back */
+		leftover = (void *)((uintptr_t)next_block + TINY_BYTES_FOR_MSIZE(coalesced_msize));
+
+		tiny_free_list_add_ptr(szone, tiny_mag_ptr, leftover, leftover_msize);
+	}
+	set_tiny_meta_header_in_use(ptr, old_msize + coalesced_msize);
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in tiny_try_realloc_in_place(), ptr=%p, msize=%d\n", ptr, old_msize + coalesced_msize);
+		malloc_printf("in tiny_try_realloc_in_place(), ptr=%p, msize=%d\n", ptr, old_msize + coalesced_msize);
 	}
 #endif
 	tiny_mag_ptr->mag_num_bytes_in_objects += TINY_BYTES_FOR_MSIZE(coalesced_msize);
@@ -1843,7 +1290,7 @@
 	node->bytes_used = (unsigned int)bytes_used;
 
 	// Emptiness discriminant
-	if (bytes_used < DENSITY_THRESHOLD(TINY_HEAP_SIZE)) {
+	if (bytes_used < DENSITY_THRESHOLD(TINY_REGION_PAYLOAD_BYTES)) {
 		/* After this reallocation the region is still sparse, so it must have been even more so before
 		 * the reallocation. That implies the region is already correctly marked. Do nothing. */
 	} else {
@@ -1852,20 +1299,13 @@
 		node->recirc_suitable = FALSE;
 	}
 
-	SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+	SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 	CHECK(szone, __PRETTY_FUNCTION__);
 	return 1;
 }
 
-static char *tiny_check_fail_msg = "*** check: incorrect tiny region ";
-
-#define TINY_CHECK_FAIL(fmt, ...) \
-	malloc_zone_check_fail(tiny_check_fail_msg, \
-			"%ld, counter=%d\n" fmt, region_index, counter, __VA_ARGS__);
-
 boolean_t
-tiny_check_region(rack_t *rack, region_t region, size_t region_index,
-		unsigned counter)
+tiny_check_region(szone_t *szone, region_t region)
 {
 	uintptr_t start, ptr, region_end;
 	boolean_t prev_free = 0;
@@ -1874,22 +1314,13 @@
 	tiny_free_list_t *free_head;
 	void *follower, *previous, *next;
 	mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(region);
-	magazine_t *tiny_mag_ptr = &(rack->magazines[mag_index]);
+	magazine_t *tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
 
 	// Assumes locked
 	CHECK_MAGAZINE_PTR_LOCKED(szone, tiny_mag_ptr, __PRETTY_FUNCTION__);
 
-	// Do not check the region if pinned_to_depot is not zero because it
-	// may not be in a consistent state (specifically, if may have a
-	// block marked as in-use that's longer than any legal allocation,
-	// which upsets get_tiny_meta_header() because it can't determine the
-	// block's length).
-	if (!REGION_TRAILER_FOR_TINY_REGION(region)->pinned_to_depot) {
-		return 1;
-	}
-
 	/* establish region limits */
-	start = (uintptr_t)TINY_REGION_HEAP_BASE(region);
+	start = (uintptr_t)TINY_REGION_ADDRESS(region);
 	ptr = start;
 	if (region == tiny_mag_ptr->mag_last_region) {
 		ptr += tiny_mag_ptr->mag_bytes_free_at_start;
@@ -1900,13 +1331,11 @@
 		if (tiny_mag_ptr->mag_bytes_free_at_start) {
 			msize = get_tiny_meta_header((void *)(ptr - TINY_QUANTUM), &is_free);
 			if (is_free || (msize != 1)) {
-				TINY_CHECK_FAIL("*** invariant broken for leader block %p - %d %d\n",
-						(void *)(ptr - TINY_QUANTUM), msize, is_free);
-				return 0;
-			}
-		}
-	}
-	region_end = (uintptr_t)TINY_REGION_HEAP_END(region);
+				malloc_printf("*** invariant broken for leader block %p - %d %d\n", ptr - TINY_QUANTUM, msize, is_free);
+			}
+		}
+	}
+	region_end = (uintptr_t)TINY_REGION_END(region);
 
 	/*
 	 * The last region may have a trailing chunk which has not been converted into inuse/freelist
@@ -1934,17 +1363,17 @@
 		 * corrupt.
 		 */
 		if (!msize) {
-			TINY_CHECK_FAIL("*** invariant broken for tiny block %p this msize=%d - size is too small\n", (void *)ptr, msize);
+			malloc_printf("*** invariant broken for tiny block %p this msize=%d - size is too small\n", ptr, msize);
 			return 0;
 		}
 
 		if (!is_free) {
 			/*
-			 * In use blocks cannot be more than NUM_TINY_SLOTS quanta large.
+			 * In use blocks cannot be more than (NUM_TINY_SLOTS - 1) quanta large.
 			 */
 			prev_free = 0;
-			if (msize > NUM_TINY_SLOTS) {
-				TINY_CHECK_FAIL("*** invariant broken for %p this tiny msize=%d - size is too large\n", (void *)ptr, msize);
+			if (msize > (NUM_TINY_SLOTS - 1)) {
+				malloc_printf("*** invariant broken for %p this tiny msize=%d - size is too large\n", ptr, msize);
 				return 0;
 			}
 			/* move to next block */
@@ -1956,7 +1385,7 @@
 			 * free block.
 			 */
 			if (prev_free) {
-				TINY_CHECK_FAIL("*** invariant broken for free block %p this tiny msize=%d: two free blocks in a row\n", (void *)ptr, msize);
+				malloc_printf("*** invariant broken for free block %p this tiny msize=%d: two free blocks in a row\n", ptr, msize);
 				return 0;
 			}
 #endif // CONFIG_RELAXED_INVARIANT_CHECKS
@@ -1965,14 +1394,14 @@
 			 * Check the integrity of this block's entry in its freelist.
 			 */
 			free_head = (tiny_free_list_t *)ptr;
-			previous = free_list_unchecksum_ptr(rack, &free_head->previous);
-			next = free_list_unchecksum_ptr(rack, &free_head->next);
+			previous = free_list_unchecksum_ptr(szone, &free_head->previous);
+			next = free_list_unchecksum_ptr(szone, &free_head->next);
 			if (previous && !tiny_meta_header_is_free(previous)) {
-				TINY_CHECK_FAIL("*** invariant broken for %p (previous %p is not a free pointer)\n", (void *)ptr, previous);
+				malloc_printf("*** invariant broken for %p (previous %p is not a free pointer)\n", ptr, previous);
 				return 0;
 			}
 			if (next && !tiny_meta_header_is_free(next)) {
-				TINY_CHECK_FAIL("*** invariant broken for %p (next in free list %p is not a free pointer)\n", (void *)ptr, next);
+				malloc_printf("*** invariant broken for %p (next in free list %p is not a free pointer)\n", ptr, next);
 				return 0;
 			}
 			/*
@@ -1980,10 +1409,10 @@
 			 */
 			follower = FOLLOWING_TINY_PTR(ptr, msize);
 			if (((uintptr_t)follower != region_end) && (get_tiny_previous_free_msize(follower) != msize)) {
-				TINY_CHECK_FAIL("*** invariant broken for tiny free %p followed by %p in region %p [%p-%p] "
-						"(end marker incorrect) should be %d; in fact %d\n",
-						(void *)ptr, follower, region, TINY_REGION_HEAP_BASE(region), (void *)region_end,
-						msize, get_tiny_previous_free_msize(follower));
+				malloc_printf(
+							  "*** invariant broken for tiny free %p followed by %p in region [%p-%p] "
+							  "(end marker incorrect) should be %d; in fact %d\n",
+							  ptr, follower, TINY_REGION_ADDRESS(region), region_end, msize, get_tiny_previous_free_msize(follower));
 				return 0;
 			}
 			/* move to next block */
@@ -1994,7 +1423,7 @@
 	 * Ensure that we scanned the entire region
 	 */
 	if (ptr != region_end) {
-		TINY_CHECK_FAIL("*** invariant broken for region end %p - %p\n", (void *)ptr, (void *)region_end);
+		malloc_printf("*** invariant broken for region end %p - %p\n", ptr, region_end);
 		return 0;
 	}
 	/*
@@ -2004,8 +1433,7 @@
 		if (tiny_mag_ptr->mag_bytes_free_at_end) {
 			msize = get_tiny_meta_header((void *)ptr, &is_free);
 			if (is_free || (msize != 1)) {
-				TINY_CHECK_FAIL("*** invariant broken for blocker block %p - %d %d\n", (void *)ptr, msize, is_free);
-				return 0;
+				malloc_printf("*** invariant broken for blocker block %p - %d %d\n", ptr, msize, is_free);
 			}
 		}
 	}
@@ -2042,7 +1470,7 @@
 	magazine_t *tiny_mag_base = NULL;
 
 	region_hash_generation_t *trg_ptr;
-	err = reader(task, (vm_address_t)szone->tiny_rack.region_generation, sizeof(region_hash_generation_t), (void **)&trg_ptr);
+	err = reader(task, (vm_address_t)szone->tiny_region_generation, sizeof(region_hash_generation_t), (void **)&trg_ptr);
 	if (err) {
 		return err;
 	}
@@ -2055,7 +1483,7 @@
 
 	if (type_mask & MALLOC_PTR_IN_USE_RANGE_TYPE) {
 		// Map in all active magazines. Do this outside the iteration over regions.
-		err = reader(task, (vm_address_t)(szone->tiny_rack.magazines), szone->tiny_rack.num_magazines * sizeof(magazine_t),
+		err = reader(task, (vm_address_t)(szone->tiny_magazines), szone->num_tiny_magazines * sizeof(magazine_t),
 					 (void **)&tiny_mag_base);
 		if (err) {
 			return err;
@@ -2065,20 +1493,24 @@
 	for (index = 0; index < num_regions; ++index) {
 		region = regions[index];
 		if (HASHRING_OPEN_ENTRY != region && HASHRING_REGION_DEALLOCATED != region) {
-			range.address = (vm_address_t)TINY_REGION_HEAP_BASE(region);
-			range.size = (vm_size_t)TINY_HEAP_SIZE;
+			range.address = (vm_address_t)TINY_REGION_ADDRESS(region);
+			range.size = (vm_size_t)TINY_REGION_SIZE;
 			if (type_mask & MALLOC_ADMIN_REGION_RANGE_TYPE) {
-				admin_range.address = TINY_REGION_METADATA(region);
+				admin_range.address = range.address + TINY_METADATA_START;
 				admin_range.size = TINY_METADATA_SIZE;
 				recorder(task, context, MALLOC_ADMIN_REGION_RANGE_TYPE, &admin_range, 1);
 			}
 			if (type_mask & (MALLOC_PTR_REGION_RANGE_TYPE | MALLOC_ADMIN_REGION_RANGE_TYPE)) {
 				ptr_range.address = range.address;
-				ptr_range.size = TINY_HEAP_SIZE;
+				ptr_range.size = NUM_TINY_BLOCKS * TINY_QUANTUM;
 				recorder(task, context, MALLOC_PTR_REGION_RANGE_TYPE, &ptr_range, 1);
 			}
 			if (type_mask & MALLOC_PTR_IN_USE_RANGE_TYPE) {
-				err = reader(task, (vm_address_t)region, (vm_size_t)TINY_REGION_SIZE, (void **)&mapped_region);
+				void *mag_last_free;
+				vm_address_t mag_last_free_ptr = 0;
+				msize_t mag_last_free_msize = 0;
+
+				err = reader(task, range.address, range.size, (void **)&mapped_region);
 				if (err) {
 					return err;
 				}
@@ -2086,18 +1518,25 @@
 				mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(mapped_region);
 				magazine_t *tiny_mag_ptr = tiny_mag_base + mag_index;
 
-				int cached_free_blocks = 0;
-#if CONFIG_TINY_CACHE
-				// Each magazine could have a pointer to a cached free block from
-				// this region. Count the regions that have such a pointer.
-				for (mag_index = 0; mag_index < szone->tiny_rack.num_magazines; mag_index++) {
-					if (region == (tiny_mag_base + mag_index)->mag_last_free_rgn) {
-						cached_free_blocks++;
+				if (DEPOT_MAGAZINE_INDEX != mag_index) {
+					mag_last_free = tiny_mag_ptr->mag_last_free;
+					if (mag_last_free) {
+						mag_last_free_ptr = (uintptr_t)mag_last_free & ~(TINY_QUANTUM - 1);
+						mag_last_free_msize = (uintptr_t)mag_last_free & (TINY_QUANTUM - 1);
+					}
+				} else {
+					for (mag_index = 0; mag_index < szone->num_tiny_magazines; mag_index++) {
+						if ((void *)range.address == (tiny_mag_base + mag_index)->mag_last_free_rgn) {
+							mag_last_free = (tiny_mag_base + mag_index)->mag_last_free;
+							if (mag_last_free) {
+								mag_last_free_ptr = (uintptr_t)mag_last_free & ~(TINY_QUANTUM - 1);
+								mag_last_free_msize = (uintptr_t)mag_last_free & (TINY_QUANTUM - 1);
+							}
+						}
 					}
 				}
-#endif // CONFIG_TINY_CACHE
-
-				block_header = TINY_BLOCK_HEADER_FOR_REGION(mapped_region);
+
+				block_header = (uint32_t *)(mapped_region + TINY_METADATA_START + sizeof(region_trailer_t));
 				in_use = TINY_INUSE_FOR_HEADER(block_header);
 				block_index = 0;
 				block_limit = NUM_TINY_BLOCKS;
@@ -2106,11 +1545,11 @@
 					block_limit -= TINY_MSIZE_FOR_BYTES(tiny_mag_ptr->mag_bytes_free_at_end);
 				}
 
-				for (; block_index < block_limit; block_index += msize) {
+				while (block_index < block_limit) {
 					vm_size_t block_offset = TINY_BYTES_FOR_MSIZE(block_index);
 					is_free = !BITARRAY_BIT(in_use, block_index);
 					if (is_free) {
-						mapped_ptr = TINY_REGION_HEAP_BASE(mapped_region) + block_offset;
+						mapped_ptr = mapped_region + block_offset;
 
 						// mapped_region, the address at which 'range' in 'task' has been
 						// mapped into our process, is not necessarily aligned to
@@ -2126,48 +1565,32 @@
 						} else {
 							msize = 1;
 						}
-					} else {
-#if CONFIG_TINY_CACHE
-						// If there are still magazines that have cached free
-						// blocks in this region, check whether this is one of
-						// them and don't return the block pointer if it is.
-						void *ptr = TINY_REGION_HEAP_BASE(region) + block_offset;
-						boolean_t block_cached = false;
-						if (cached_free_blocks) {
-							for (mag_index = 0; mag_index < szone->tiny_rack.num_magazines; mag_index++) {
-								if (ptr == (tiny_mag_base + mag_index)->mag_last_free) {
-									block_cached = true;
-									cached_free_blocks--;
-									msize = (tiny_mag_base + mag_index)->mag_last_free_msize;
-									break;
-								}
-							}
-						}
-						if (block_cached) {
-							if (!msize) {
-								return KERN_FAILURE; // Somethings amiss. Avoid looping at this block_index.
-							}
-							continue;
-						}
-#endif // CONFIG_TINY_CACHE
+
+					} else if (range.address + block_offset != mag_last_free_ptr) {
 						msize = 1;
 						bit = block_index + 1;
 						while (!BITARRAY_BIT(block_header, bit)) {
 							bit++;
 							msize++;
 						}
-						buffer[count].address = (vm_address_t)TINY_REGION_HEAP_BASE(region) + block_offset;
+						buffer[count].address = range.address + block_offset;
 						buffer[count].size = TINY_BYTES_FOR_MSIZE(msize);
 						count++;
 						if (count >= MAX_RECORDER_BUFFER) {
 							recorder(task, context, MALLOC_PTR_IN_USE_RANGE_TYPE, buffer, count);
 							count = 0;
 						}
+					} else {
+						// Block is not free but it matches mag_last_free_ptr so even
+						// though it is not marked free in the bitmap, we treat it as if
+						// it is and move on
+						msize = mag_last_free_msize;
 					}
 
 					if (!msize) {
 						return KERN_FAILURE; // Somethings amiss. Avoid looping at this block_index.
 					}
+					block_index += msize;
 				}
 				if (count) {
 					recorder(task, context, MALLOC_PTR_IN_USE_RANGE_TYPE, buffer, count);
@@ -2180,11 +1603,11 @@
 }
 
 void *
-tiny_malloc_from_free_list(rack_t *rack, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
+tiny_malloc_from_free_list(szone_t *szone, magazine_t *tiny_mag_ptr, mag_index_t mag_index, msize_t msize)
 {
 	tiny_free_list_t *ptr;
 	msize_t this_msize;
-	grain_t slot = tiny_slot_from_msize(msize);
+	grain_t slot = msize - 1;
 	free_list_t *free_list = tiny_mag_ptr->mag_free_list;
 	free_list_t *the_slot = free_list + slot;
 	tiny_free_list_t *next;
@@ -2204,7 +1627,7 @@
 	//
 	ptr = the_slot->p;
 	if (ptr) {
-		next = free_list_unchecksum_ptr(rack, &ptr->next);
+		next = free_list_unchecksum_ptr(szone, &ptr->next);
 		if (next) {
 			next->previous = ptr->previous;
 		} else {
@@ -2214,12 +1637,9 @@
 		this_msize = msize;
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_free_list(), exact match ptr=%p, this_msize=%d\n", ptr, this_msize);
-		}
-#endif
-		tiny_update_region_free_list_for_remove(slot, ptr, next);
-		tiny_check_and_zero_inline_meta_from_freelist(rack, ptr, msize);
-
+			malloc_printf("in tiny_malloc_from_free_list(), exact match ptr=%p, this_msize=%d\n", ptr, this_msize);
+		}
+#endif
 		goto return_tiny_alloc;
 	}
 
@@ -2236,13 +1656,13 @@
 	}
 
 	slot = BITMAPV_CTZ(bitmap);
-	limit = free_list + NUM_TINY_SLOTS;
+	limit = free_list + NUM_TINY_SLOTS - 1;
 	free_list += slot;
 
 	if (free_list < limit) {
 		ptr = free_list->p;
 		if (ptr) {
-			next = free_list_unchecksum_ptr(rack, &ptr->next);
+			next = free_list_unchecksum_ptr(szone, &ptr->next);
 			free_list->p = next;
 			if (next) {
 				next->previous = ptr->previous;
@@ -2250,56 +1670,46 @@
 				BITMAPV_CLR(tiny_mag_ptr->mag_bitmap, slot);
 			}
 			this_msize = get_tiny_free_size(ptr);
-			tiny_update_region_free_list_for_remove(slot, ptr, next);
-			tiny_check_and_zero_inline_meta_from_freelist(rack, ptr, this_msize);
 			goto add_leftover_and_proceed;
 		}
 #if DEBUG_MALLOC
-		malloc_report(ASL_LEVEL_ERR, "in tiny_malloc_from_free_list(), mag_bitmap out of sync, slot=%d\n", slot);
+		malloc_printf("in tiny_malloc_from_free_list(), mag_bitmap out of sync, slot=%d\n", slot);
 #endif
 	}
 
 	// We are now looking at the last slot, which contains blocks equal to, or
-	// due to coalescing of free blocks, larger than NUM_TINY_SLOTS * tiny quantum size.
+	// due to coalescing of free blocks, larger than (NUM_TINY_SLOTS - 1) * tiny quantum size.
 	// If the last freelist is not empty, and the head contains a block that is
 	// larger than our request, then the remainder is put back on the free list.
 	ptr = limit->p;
 	if (ptr) {
 		this_msize = get_tiny_free_size(ptr);
-		next = free_list_unchecksum_ptr(rack, &ptr->next);
-		if (this_msize - msize > NUM_TINY_SLOTS) {
+		next = free_list_unchecksum_ptr(szone, &ptr->next);
+		if (this_msize - msize >= NUM_TINY_SLOTS) {
 			// the leftover will go back to the free list, so we optimize by
 			// modifying the free list rather than a pop and push of the head
 			leftover_msize = this_msize - msize;
 			leftover_ptr = (tiny_free_list_t *)((unsigned char *)ptr + TINY_BYTES_FOR_MSIZE(msize));
-
-			tiny_free_list_t tmp_ptr = *ptr;
-			tiny_check_and_zero_inline_meta_from_freelist(rack, ptr, this_msize);
-
 			limit->p = leftover_ptr;
 			if (next) {
-				next->previous.u = free_list_checksum_ptr(rack, leftover_ptr);
-			}
-			leftover_ptr->previous = tmp_ptr.previous;
-			leftover_ptr->next = tmp_ptr.next;
+				next->previous.u = free_list_checksum_ptr(szone, leftover_ptr);
+			}
+			leftover_ptr->previous = ptr->previous;
+			leftover_ptr->next = ptr->next;
 			set_tiny_meta_header_free(leftover_ptr, leftover_msize);
 #if DEBUG_MALLOC
 			if (LOG(szone, ptr)) {
-				malloc_report(ASL_LEVEL_INFO,
+				malloc_printf(
 							  "in tiny_malloc_from_free_list(), last slot ptr=%p, msize=%d this_msize=%d\n", ptr, msize, this_msize);
 			}
 #endif
 			this_msize = msize;
-			tiny_update_region_free_list_for_remove(NUM_TINY_SLOTS, ptr, leftover_ptr);
-
 			goto return_tiny_alloc;
 		}
 		if (next) {
 			next->previous = ptr->previous;
 		}
 		limit->p = next;
-		tiny_update_region_free_list_for_remove(slot, ptr, next);
-		tiny_check_and_zero_inline_meta_from_freelist(rack, ptr, this_msize);
 		goto add_leftover_and_proceed;
 		/* NOTREACHED */
 	}
@@ -2307,7 +1717,7 @@
 try_tiny_malloc_from_end:
 	// Let's see if we can use tiny_mag_ptr->mag_bytes_free_at_end
 	if (tiny_mag_ptr->mag_bytes_free_at_end >= TINY_BYTES_FOR_MSIZE(msize)) {
-		ptr = (tiny_free_list_t *)((uintptr_t)TINY_REGION_HEAP_END(tiny_mag_ptr->mag_last_region) - tiny_mag_ptr->mag_bytes_free_at_end);
+		ptr = (tiny_free_list_t *)((uintptr_t)TINY_REGION_END(tiny_mag_ptr->mag_last_region) - tiny_mag_ptr->mag_bytes_free_at_end);
 		tiny_mag_ptr->mag_bytes_free_at_end -= TINY_BYTES_FOR_MSIZE(msize);
 		if (tiny_mag_ptr->mag_bytes_free_at_end) {
 			// let's add an in use block after ptr to serve as boundary
@@ -2316,7 +1726,7 @@
 		this_msize = msize;
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_free_list(), from end ptr=%p, msize=%d\n", ptr, msize);
+			malloc_printf("in tiny_malloc_from_free_list(), from end ptr=%p, msize=%d\n", ptr, msize);
 		}
 #endif
 		goto return_tiny_alloc;
@@ -2324,7 +1734,7 @@
 #if CONFIG_ASLR_INTERNAL
 	// Try from start if nothing left at end
 	if (tiny_mag_ptr->mag_bytes_free_at_start >= TINY_BYTES_FOR_MSIZE(msize)) {
-		ptr = (tiny_free_list_t *)(TINY_REGION_HEAP_BASE(tiny_mag_ptr->mag_last_region) + tiny_mag_ptr->mag_bytes_free_at_start -
+		ptr = (tiny_free_list_t *)(TINY_REGION_ADDRESS(tiny_mag_ptr->mag_last_region) + tiny_mag_ptr->mag_bytes_free_at_start -
 							  TINY_BYTES_FOR_MSIZE(msize));
 		tiny_mag_ptr->mag_bytes_free_at_start -= TINY_BYTES_FOR_MSIZE(msize);
 		if (tiny_mag_ptr->mag_bytes_free_at_start) {
@@ -2334,7 +1744,7 @@
 		this_msize = msize;
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_free_list(), from start ptr=%p, msize=%d\n", ptr, msize);
+			malloc_printf("in tiny_malloc_from_free_list(), from start ptr=%p, msize=%d\n", ptr, msize);
 		}
 #endif
 		goto return_tiny_alloc;
@@ -2344,16 +1754,14 @@
 
 add_leftover_and_proceed:
 	if (!this_msize || (this_msize > msize)) {
-		// XXX This works even when (this_msize == 0) because the unsigned
-		// subtraction wraps around to the correct result
 		leftover_msize = this_msize - msize;
 		leftover_ptr = (tiny_free_list_t *)((unsigned char *)ptr + TINY_BYTES_FOR_MSIZE(msize));
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_free_list(), adding leftover ptr=%p, this_msize=%d\n", ptr, this_msize);
-		}
-#endif
-		tiny_free_list_add_ptr(rack, tiny_mag_ptr, leftover_ptr, leftover_msize);
+			malloc_printf("in tiny_malloc_from_free_list(), adding leftover ptr=%p, this_msize=%d\n", ptr, this_msize);
+		}
+#endif
+		tiny_free_list_add_ptr(szone, tiny_mag_ptr, leftover_ptr, leftover_msize);
 		this_msize = msize;
 	}
 
@@ -2361,27 +1769,23 @@
 	tiny_mag_ptr->mag_num_objects++;
 	tiny_mag_ptr->mag_num_bytes_in_objects += TINY_BYTES_FOR_MSIZE(this_msize);
 
-	// Check that the region cookie is intact and update the region's bytes in use count
-	tiny_region_t region = TINY_REGION_FOR_PTR(ptr);
-	region_check_cookie(region, &REGION_COOKIE_FOR_TINY_REGION(region));
-
-	region_trailer_t *trailer = REGION_TRAILER_FOR_TINY_REGION(region);
-	size_t bytes_used = trailer->bytes_used + TINY_BYTES_FOR_MSIZE(this_msize);
-	trailer->bytes_used = (unsigned int)bytes_used;
-	trailer->objects_in_use++;
+	// Update this region's bytes in use count
+	region_trailer_t *node = REGION_TRAILER_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr));
+	size_t bytes_used = node->bytes_used + TINY_BYTES_FOR_MSIZE(this_msize);
+	node->bytes_used = (unsigned int)bytes_used;
 
 	// Emptiness discriminant
-	if (bytes_used < DENSITY_THRESHOLD(TINY_HEAP_SIZE)) {
+	if (bytes_used < DENSITY_THRESHOLD(TINY_REGION_PAYLOAD_BYTES)) {
 		/* After this allocation the region is still sparse, so it must have been even more so before
 		 * the allocation. That implies the region is already correctly marked. Do nothing. */
 	} else {
 		/* Region has crossed threshold from sparsity to density. Mark it not "suitable" on the
 		 * recirculation candidates list. */
-		trailer->recirc_suitable = FALSE;
+		node->recirc_suitable = FALSE;
 	}
 #if DEBUG_MALLOC
 	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_from_free_list(), ptr=%p, this_msize=%d, msize=%d\n", ptr, this_msize, msize);
+		malloc_printf("in tiny_malloc_from_free_list(), ptr=%p, this_msize=%d, msize=%d\n", ptr, this_msize, msize);
 	}
 #endif
 	if (this_msize > 1) {
@@ -2393,44 +1797,44 @@
 }
 
 void *
-tiny_malloc_should_clear(rack_t *rack, msize_t msize, boolean_t cleared_requested)
+tiny_malloc_should_clear(szone_t *szone, msize_t msize, boolean_t cleared_requested)
 {
 	void *ptr;
-	mag_index_t mag_index = rack_get_thread_index(rack) % rack->num_magazines;
-	magazine_t *tiny_mag_ptr = &(rack->magazines[mag_index]);
-
-	MALLOC_TRACE(TRACE_tiny_malloc, (uintptr_t)rack, TINY_BYTES_FOR_MSIZE(msize), (uintptr_t)tiny_mag_ptr, cleared_requested);
+	mag_index_t mag_index = mag_get_thread_index(szone);
+	magazine_t *tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
+
+	MALLOC_TRACE(TRACE_tiny_malloc, (uintptr_t)szone, TINY_BYTES_FOR_MSIZE(msize), (uintptr_t)tiny_mag_ptr, cleared_requested);
 
 #if DEBUG_MALLOC
 	if (DEPOT_MAGAZINE_INDEX == mag_index) {
-		malloc_zone_error(rack->debug_flags, true, "malloc called for magazine index -1\n");
+		szone_error(szone, 1, "malloc called for magazine index -1", NULL, NULL);
 		return (NULL);
 	}
 
 	if (!msize) {
-		malloc_zone_error(rack->debug_flags, true, "invariant broken (!msize) in allocation (region)\n");
+		szone_error(szone, 1, "invariant broken (!msize) in allocation (region)", NULL, NULL);
 		return (NULL);
 	}
 #endif
 
-	SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
+	SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
 
 #if CONFIG_TINY_CACHE
 	ptr = tiny_mag_ptr->mag_last_free;
 
-	if (tiny_mag_ptr->mag_last_free_msize == msize) {
+	if ((((uintptr_t)ptr) & (TINY_QUANTUM - 1)) == msize) {
 		// we have a winner
 		tiny_mag_ptr->mag_last_free = NULL;
-		tiny_mag_ptr->mag_last_free_msize = 0;
 		tiny_mag_ptr->mag_last_free_rgn = NULL;
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 		CHECK(szone, __PRETTY_FUNCTION__);
-
-		tiny_check_zero_or_clear(ptr, msize, cleared_requested);
-
+		ptr = (void *)((uintptr_t)ptr & ~(TINY_QUANTUM - 1));
+		if (cleared_requested) {
+			memset(ptr, 0, TINY_BYTES_FOR_MSIZE(msize));
+		}
 #if DEBUG_MALLOC
 		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in tiny_malloc_should_clear(), tiny cache ptr=%p, msize=%d\n", ptr, msize);
+			malloc_printf("in tiny_malloc_should_clear(), tiny cache ptr=%p, msize=%d\n", ptr, msize);
 		}
 #endif
 		return ptr;
@@ -2438,25 +1842,27 @@
 #endif /* CONFIG_TINY_CACHE */
 
 	while (1) {
-		ptr = tiny_malloc_from_free_list(rack, tiny_mag_ptr, mag_index, msize);
+		ptr = tiny_malloc_from_free_list(szone, tiny_mag_ptr, mag_index, msize);
 		if (ptr) {
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 			CHECK(szone, __PRETTY_FUNCTION__);
-			tiny_check_zero_or_clear(ptr, msize, cleared_requested);
+			if (cleared_requested) {
+				memset(ptr, 0, TINY_BYTES_FOR_MSIZE(msize));
+			}
 			return ptr;
 		}
 
-#if CONFIG_RECIRC_DEPOT
-		if (tiny_get_region_from_depot(rack, tiny_mag_ptr, mag_index, msize)) {
-			ptr = tiny_malloc_from_free_list(rack, tiny_mag_ptr, mag_index, msize);
+		if (tiny_get_region_from_depot(szone, tiny_mag_ptr, mag_index, msize)) {
+			ptr = tiny_malloc_from_free_list(szone, tiny_mag_ptr, mag_index, msize);
 			if (ptr) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				CHECK(szone, __PRETTY_FUNCTION__);
-				tiny_check_zero_or_clear(ptr, msize, cleared_requested);
+				if (cleared_requested) {
+					memset(ptr, 0, TINY_BYTES_FOR_MSIZE(msize));
+				}
 				return ptr;
 			}
 		}
-#endif // CONFIG_RECIRC_DEPOT
 
 		// The magazine is exhausted. A new region (heap) must be allocated to satisfy this call to malloc().
 		// The allocation, an mmap() system call, will be performed outside the magazine spin locks by the first
@@ -2470,100 +1876,54 @@
 			// time to create a new region (do this outside the magazine lock)
 			tiny_mag_ptr->alloc_underway = TRUE;
 			OSMemoryBarrier();
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-			fresh_region = mvm_allocate_pages(TINY_REGION_SIZE,
-					TINY_BLOCKS_ALIGN,
-					MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags),
-					VM_MEMORY_MALLOC_TINY);
-			SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
-
-			// DTrace USDT Probe
-			MAGMALLOC_ALLOCREGION(TINY_SZONE_FROM_RACK(rack), (int)mag_index, fresh_region, TINY_REGION_SIZE);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+			fresh_region = allocate_pages_securely(szone, TINY_REGION_SIZE, TINY_BLOCKS_ALIGN, VM_MEMORY_MALLOC_TINY);
+			SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
+
+			MAGMALLOC_ALLOCREGION((void *)szone, (int)mag_index, fresh_region, TINY_REGION_SIZE); // DTrace USDT Probe
 
 			if (!fresh_region) { // out of memory!
 				tiny_mag_ptr->alloc_underway = FALSE;
 				OSMemoryBarrier();
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				return NULL;
 			}
 
-			region_set_cookie(&REGION_COOKIE_FOR_TINY_REGION(fresh_region));
-			ptr = tiny_malloc_from_region_no_lock(rack, tiny_mag_ptr, mag_index, msize, fresh_region);
-
-			// we don't clear or zero-check because this freshly allocated space
-			// is pristine
+			ptr = tiny_malloc_from_region_no_lock(szone, tiny_mag_ptr, mag_index, msize, fresh_region);
+
+			// we don't clear because this freshly allocated space is pristine
 			tiny_mag_ptr->alloc_underway = FALSE;
 			OSMemoryBarrier();
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 			CHECK(szone, __PRETTY_FUNCTION__);
 			return ptr;
 		} else {
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 			yield();
-			SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
+			SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
 		}
 	}
 	/* NOTREACHED */
 }
 
-size_t
-tiny_size(rack_t *rack, const void *ptr)
-{
-	if (tiny_region_for_ptr_no_lock(rack, ptr)) {
-		if (TINY_INDEX_FOR_PTR(ptr) >= NUM_TINY_BLOCKS) {
-malloc_printf("NO ZONE for ptr %p\n", ptr);
-			return 0;
-		}
-
-		boolean_t is_free;
-		msize_t msize = get_tiny_meta_header(ptr, &is_free);
-		if (is_free) {
-			return 0;
-		}
-
-#if CONFIG_TINY_CACHE
-		{
-			mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr));
-			if (DEPOT_MAGAZINE_INDEX != mag_index) {
-				magazine_t *tiny_mag_ptr = &rack->magazines[mag_index];
-
-				if (msize < TINY_QUANTUM && ptr == tiny_mag_ptr->mag_last_free) {
-					return 0;
-				}
-			} else {
-				for (mag_index = 0; mag_index < rack->num_magazines; mag_index++) {
-					magazine_t *tiny_mag_ptr = &(rack->magazines[mag_index]);
-
-					if (msize < TINY_QUANTUM && ptr == tiny_mag_ptr->mag_last_free) {
-						return 0;
-					}
-				}
-			}
-		}
-#endif
-		return TINY_BYTES_FOR_MSIZE(msize);
-	}
-
-	return 0;
-}
-
 static MALLOC_NOINLINE void
-free_tiny_botch(rack_t *rack, tiny_free_list_t *ptr)
-{
-	malloc_zone_error(rack->debug_flags, true, "Double free of object %p\n", ptr);
+free_tiny_botch(szone_t *szone, tiny_free_list_t *ptr)
+{
+	mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(TINY_REGION_FOR_PTR(ptr));
+	magazine_t *tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
+	SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+	szone_error(szone, 1, "double free", ptr, NULL);
 }
 
 void
-free_tiny(rack_t *rack, void *ptr, region_t tiny_region, size_t known_size,
-		boolean_t partial_free)
+free_tiny(szone_t *szone, void *ptr, region_t tiny_region, size_t known_size)
 {
 	msize_t msize;
 	boolean_t is_free;
 	mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(tiny_region);
-	magazine_t *tiny_mag_ptr = &(rack->magazines[mag_index]);
-	uint32_t flags = 0;
-
-	MALLOC_TRACE(TRACE_tiny_free, (uintptr_t)rack, (uintptr_t)ptr, (uintptr_t)tiny_mag_ptr, known_size);
+	magazine_t *tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
+
+	MALLOC_TRACE(TRACE_tiny_free, (uintptr_t)szone, (uintptr_t)ptr, (uintptr_t)tiny_mag_ptr, known_size);
 
 	// ptr is known to be in tiny_region
 	if (known_size) {
@@ -2571,58 +1931,48 @@
 	} else {
 		msize = get_tiny_meta_header(ptr, &is_free);
 		if (is_free) {
-			free_tiny_botch(rack, ptr);
+			free_tiny_botch(szone, ptr);
 			return;
 		}
 	}
 #if DEBUG_MALLOC
 	if (!msize) {
-		malloc_report(ASL_LEVEL_ERR, "*** free_tiny() block in use is too large: %p\n", ptr);
+		malloc_printf("*** free_tiny() block in use is too large: %p\n", ptr);
 		return;
 	}
 #endif
 
-	if (malloc_zero_policy == MALLOC_ZERO_ON_FREE) {
-		memset(ptr, '\0', TINY_BYTES_FOR_MSIZE(msize));
-	}
-
-	SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
+	SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
 
 #if CONFIG_TINY_CACHE
 	// Depot does not participate in CONFIG_TINY_CACHE since it can't be directly malloc()'d
-	if (DEPOT_MAGAZINE_INDEX != mag_index && !partial_free) {
+	if (DEPOT_MAGAZINE_INDEX != mag_index) {
 		if (msize < TINY_QUANTUM) {					  // to see if the bits fit in the last 4 bits
 			void *ptr2 = tiny_mag_ptr->mag_last_free; // Might be NULL
-			msize_t msize2 = tiny_mag_ptr->mag_last_free_msize;
 			region_t rgn2 = tiny_mag_ptr->mag_last_free_rgn;
 
 			/* check that we don't already have this pointer in the cache */
-			if (ptr == ptr2) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-				free_tiny_botch(rack, ptr);
+			if (ptr == (void *)((uintptr_t)ptr2 & ~(TINY_QUANTUM - 1))) {
+				free_tiny_botch(szone, ptr);
 				return;
 			}
 
-			if (malloc_zero_policy != MALLOC_ZERO_ON_FREE) {
-				if ((rack->debug_flags & MALLOC_DO_SCRIBBLE) && msize) {
-					memset(ptr, SCRABBLE_BYTE, TINY_BYTES_FOR_MSIZE(msize));
-				}
-			}
-
-			tiny_mag_ptr->mag_last_free = ptr;
-			tiny_mag_ptr->mag_last_free_msize = msize;
+			if ((szone->debug_flags & MALLOC_DO_SCRIBBLE) && msize) {
+				memset(ptr, SCRABBLE_BYTE, TINY_BYTES_FOR_MSIZE(msize));
+			}
+
+			tiny_mag_ptr->mag_last_free = (void *)(((uintptr_t)ptr) | msize);
 			tiny_mag_ptr->mag_last_free_rgn = tiny_region;
 
 			if (!ptr2) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				CHECK(szone, __PRETTY_FUNCTION__);
 				return;
 			}
 
-			msize = msize2;
-			ptr = ptr2;
+			msize = (uintptr_t)ptr2 & (TINY_QUANTUM - 1);
+			ptr = (void *)(((uintptr_t)ptr2) & ~(TINY_QUANTUM - 1));
 			tiny_region = rgn2;
-			flags |= TINY_FREE_FLAG_FROM_CACHE;
 		}
 	}
 #endif /* CONFIG_TINY_CACHE */
@@ -2635,207 +1985,66 @@
 	mag_index_t refreshed_index;
 
 	while (mag_index != (refreshed_index = trailer->mag_index)) { // Note assignment
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
+
 		mag_index = refreshed_index;
-		tiny_mag_ptr = &(rack->magazines[mag_index]);
-		SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
-	}
-
-	if (partial_free) {
-		flags |= TINY_FREE_FLAG_PARTIAL;
-	}
-
-	if (tiny_free_no_lock(rack, tiny_mag_ptr, mag_index, tiny_region, ptr,
-			msize, flags)) {
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
+		SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
+	}
+
+	if (tiny_free_no_lock(szone, tiny_mag_ptr, mag_index, tiny_region, ptr, msize)) {
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 	}
 
 	CHECK(szone, __PRETTY_FUNCTION__);
 }
 
-unsigned
-tiny_batch_malloc(szone_t *szone, size_t size, void **results, unsigned count)
-{
-	msize_t msize = TINY_MSIZE_FOR_BYTES(size + TINY_QUANTUM - 1);
-	unsigned found = 0;
-
-	mag_index_t mag_index = rack_get_thread_index(&szone->tiny_rack) % szone->tiny_rack.num_magazines;
-	magazine_t *tiny_mag_ptr = &(szone->tiny_rack.magazines[mag_index]);
-
-	// make sure to return objects at least one quantum in size
-	if (!msize) {
-		msize = 1;
-	}
-
-	CHECK(szone, __PRETTY_FUNCTION__);
-
-	// We must lock the zone now, since tiny_malloc_from_free_list assumes that
-	// the caller has done so.
-	SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
-
-	// with the zone locked, allocate objects from the free list until all
-	// sufficiently large objects have been exhausted, or we have met our quota
-	// of objects to allocate.
-	while (found < count) {
-		void *ptr = tiny_malloc_from_free_list(&szone->tiny_rack, tiny_mag_ptr, mag_index, msize);
-		if (!ptr) {
-			break;
-		}
-
-		*results++ = ptr;
-		found++;
-	}
-	SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-	return found;
-}
-
 void
-tiny_batch_free(szone_t *szone, void **to_be_freed, unsigned count)
-{
-	unsigned cc = 0;
-	void *ptr;
-	region_t tiny_region = NULL;
-	boolean_t is_free;
-	msize_t msize;
-	magazine_t *tiny_mag_ptr = NULL;
-	mag_index_t mag_index = -1;
-
-	// frees all the pointers in to_be_freed
-	// note that to_be_freed may be overwritten during the process
-	if (!count) {
-		return;
-	}
-
-	CHECK(szone, __PRETTY_FUNCTION__);
-	while (cc < count) {
-		ptr = to_be_freed[cc];
-		if (ptr) {
-			if (NULL == tiny_region || tiny_region != TINY_REGION_FOR_PTR(ptr)) { // region same as last iteration?
-				if (tiny_mag_ptr) {												  // non-NULL iff magazine lock taken
-					SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-					tiny_mag_ptr = NULL;
-				}
-
-				tiny_region = tiny_region_for_ptr_no_lock(&szone->tiny_rack, ptr);
-
-				if (tiny_region) {
-					tiny_mag_ptr = mag_lock_zine_for_region_trailer(szone->tiny_rack.magazines,
-							REGION_TRAILER_FOR_TINY_REGION(tiny_region),
-							MAGAZINE_INDEX_FOR_TINY_REGION(tiny_region));
-					mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(tiny_region);
-				}
-			}
-			if (tiny_region) {
-				// this is a tiny pointer
-				if (TINY_INDEX_FOR_PTR(ptr) >= NUM_TINY_BLOCKS) {
-					break; // pointer to metadata; let the standard free deal with it
-				}
-				msize = get_tiny_meta_header(ptr, &is_free);
-				if (is_free) {
-					break; // a double free; let the standard free deal with it
-				}
-				if (malloc_zero_policy == MALLOC_ZERO_ON_FREE) {
-					memset(ptr, '\0', TINY_BYTES_FOR_MSIZE(msize));
-				}
-				if (!tiny_free_no_lock(&szone->tiny_rack, tiny_mag_ptr, mag_index, tiny_region, ptr, msize, 0)) {
-					// Arrange to re-acquire magazine lock
-					tiny_mag_ptr = NULL;
-					tiny_region = NULL;
-				}
-				to_be_freed[cc] = NULL;
-			} else {
-				// No region in this zone claims ptr; let the standard free deal with it
-				break;
-			}
-		}
-		cc++;
-	}
-
-	if (tiny_mag_ptr) {
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-		tiny_mag_ptr = NULL;
-	}
-}
-
-
-void
-print_tiny_free_list(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack)
+print_tiny_free_list(szone_t *szone)
 {
 	tiny_free_list_t *ptr;
 	_SIMPLE_STRING b = _simple_salloc();
 	mag_index_t mag_index;
 
 	if (b) {
-		rack_t *mapped_rack;
-		magazine_t *mapped_magazines;
-		if (reader(task, (vm_address_t)rack, sizeof(struct rack_s),
-				(void **)&mapped_rack)) {
-			printer("Failed to map tiny rack\n");
-			return;
-		}
-		_simple_sappend(b, "Tiny free sizes:\n");
-		if (reader(task, (vm_address_t)mapped_rack->magazines,
-				mapped_rack->num_magazines * sizeof(magazine_t),
-				(void **)&mapped_magazines)) {
-			printer("Failed to map tiny rack magazines\n");
-			return;
-		}
-
-		for (mag_index = -1; mag_index < mapped_rack->num_magazines; mag_index++) {
+		_simple_sappend(b, "tiny free sizes:\n");
+		for (mag_index = -1; mag_index < szone->num_tiny_magazines; mag_index++) {
 			grain_t slot = 0;
-			if (mag_index == -1) {
-				_simple_sprintf(b, "\tRecirc depot: ");
-			} else {
-				_simple_sprintf(b, "\tMagazine %d: ", mag_index);
-			}
-			while (slot <= NUM_TINY_SLOTS) {
-				ptr = mapped_magazines[mag_index].mag_free_list[slot].p;
+			_simple_sprintf(b, "\tMagazine %d: ", mag_index);
+			while (slot < NUM_TINY_SLOTS) {
+				ptr = szone->tiny_magazines[mag_index].mag_free_list[slot].p;
 				if (ptr) {
-					_simple_sprintf(b, "%s%y[%d]; ",
-							(slot == NUM_TINY_SLOTS) ? ">=" : "",
-							(slot + 1) * TINY_QUANTUM,
-							free_list_count(task, reader, printer, mapped_rack,
-									(free_list_t){ .p = ptr }));
+					_simple_sprintf(b, "%s%y[%d]; ", (slot == NUM_TINY_SLOTS - 1) ? ">=" : "", (slot + 1) * TINY_QUANTUM,
+									free_list_count(szone, (free_list_t){ .p = ptr }));
 				}
 				slot++;
 			}
 			_simple_sappend(b, "\n");
 		}
-		printer("%s\n", _simple_string(b));
+		_malloc_printf(MALLOC_PRINTF_NOLOG | MALLOC_PRINTF_NOPREFIX, "%s\n", _simple_string(b));
 		_simple_sfree(b);
 	}
 }
 
 void
-print_tiny_region(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, int level, region_t region,
-		size_t bytes_at_start, size_t bytes_at_end)
+print_tiny_region(boolean_t verbose, region_t region, size_t bytes_at_start, size_t bytes_at_end)
 {
 	unsigned counts[1024];
 	unsigned in_use = 0;
-	uintptr_t start = (uintptr_t)TINY_REGION_HEAP_BASE(region);
+	uintptr_t start = (uintptr_t)TINY_REGION_ADDRESS(region);
 	uintptr_t current = start + bytes_at_start;
-	uintptr_t limit = (uintptr_t)TINY_REGION_HEAP_END(region) - bytes_at_end;
-	uintptr_t mapped_start;
+	uintptr_t limit = (uintptr_t)TINY_REGION_END(region) - bytes_at_end;
 	boolean_t is_free;
 	msize_t msize;
 	unsigned ci;
 	_SIMPLE_STRING b;
 	uintptr_t pgTot = 0;
 
-	if (reader(task, (vm_address_t)start, TINY_REGION_SIZE,
-            (void **)&mapped_start)) {
-        printer("Failed to map tiny region at %p\n", start);
-        return;
-    }
-    off_t start_offset = mapped_start - start;
-    region_t mapped_region = (region_t)mapped_start;
-
 	if (region == HASHRING_REGION_DEALLOCATED) {
 		if ((b = _simple_salloc()) != NULL) {
 			_simple_sprintf(b, "Tiny region [unknown address] was returned to the OS\n");
-			printer("%s\n", _simple_string(b));
+			_malloc_printf(MALLOC_PRINTF_NOLOG | MALLOC_PRINTF_NOPREFIX, "%s\n", _simple_string(b));
 			_simple_sfree(b);
 		}
 		return;
@@ -2843,7 +2052,7 @@
 
 	memset(counts, 0, sizeof(counts));
 	while (current < limit) {
-		msize = get_tiny_meta_header_offset((void *)current, start_offset, &is_free);
+		msize = get_tiny_meta_header((void *)current, &is_free);
 		if (is_free && !msize && (current == start)) {
 			// first block is all free
 			uintptr_t pgLo = round_page_quanta(start + sizeof(tiny_free_list_t) + sizeof(msize_t));
@@ -2855,13 +2064,13 @@
 			break;
 		}
 		if (!msize) {
-			printer("*** error with %p: msize=%d\n", (void *)current, (unsigned)msize);
+			malloc_printf("*** error with %p: msize=%d\n", (void *)current, (unsigned)msize);
 			break;
 		}
 		if (!is_free) {
 			// block in use
 			if (msize > NUM_TINY_SLOTS) {
-				printer("*** error at %p msize for in_use is %d\n", (void *)current, msize);
+				malloc_printf("*** error at %p msize for in_use is %d\n", (void *)current, msize);
 			}
 			if (msize < 1024) {
 				counts[msize]++;
@@ -2878,126 +2087,72 @@
 		current += TINY_BYTES_FOR_MSIZE(msize);
 	}
 	if ((b = _simple_salloc()) != NULL) {
-		mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(mapped_region);
-		_simple_sprintf(b, "Tiny region [%p-%p, %y] \t", (void *)start, TINY_REGION_HEAP_END(region), (int)TINY_REGION_SIZE);
-        if (mag_index == DEPOT_MAGAZINE_INDEX) {
-            _simple_sprintf(b, "Recirc depot \t");
-        } else {
-		    _simple_sprintf(b, "Magazine=%d \t", mag_index);
-        }
-		_simple_sprintf(b, "Allocations in use=%d \t Bytes in use=%ly (%d%%) \t",
-				in_use, BYTES_USED_FOR_TINY_REGION(mapped_region),
-				(int)(100.0F * BYTES_USED_FOR_TINY_REGION(mapped_region))/TINY_REGION_SIZE);
+		_simple_sprintf(b, "Tiny region [%p-%p, %y] \t", (void *)start, TINY_REGION_END(region), (int)TINY_REGION_SIZE);
+		_simple_sprintf(b, "Magazine=%d \t", MAGAZINE_INDEX_FOR_TINY_REGION(region));
+		_simple_sprintf(b, "Allocations in use=%d \t Bytes in use=%ly \t", in_use, BYTES_USED_FOR_TINY_REGION(region));
 		if (bytes_at_end || bytes_at_start) {
 			_simple_sprintf(b, "Untouched=%ly ", bytes_at_end + bytes_at_start);
 		}
-		if (mag_index == DEPOT_MAGAZINE_INDEX) {
+		if (DEPOT_MAGAZINE_INDEX == MAGAZINE_INDEX_FOR_TINY_REGION(region)) {
 			_simple_sprintf(b, "Advised MADV_FREE=%ly", pgTot);
 		} else {
 			_simple_sprintf(b, "Fragments subject to reclamation=%ly", pgTot);
-#if CONFIG_RECIRC_DEPOT
-			_simple_sprintf(b, tiny_region_below_recirc_threshold(mapped_region) ?
-					"\tEmpty enough to be moved to recirc depot" :
-					"\tNot empty enough to be moved to recirc depot");
-#endif // CONFIG_RECIRC_DEPOT
-		}
-		if (level >= MALLOC_VERBOSE_PRINT_LEVEL && in_use) {
+		}
+		if (verbose && in_use) {
 			_simple_sappend(b, "\n\tSizes in use: ");
 			for (ci = 0; ci < 1024; ci++) {
 				if (counts[ci]) {
-					_simple_sprintf(b, "%y[%d] ", TINY_BYTES_FOR_MSIZE(ci), counts[ci]);
+					_simple_sprintf(b, "%d[%d] ", TINY_BYTES_FOR_MSIZE(ci), counts[ci]);
 				}
 			}
 		}
-		printer("%s\n", _simple_string(b));
+		_malloc_printf(MALLOC_PRINTF_NOLOG | MALLOC_PRINTF_NOPREFIX, "%s\n", _simple_string(b));
 		_simple_sfree(b);
 	}
 }
 
-static char *tiny_freelist_fail_msg = "check: tiny free list incorrect ";
-
-#define TINY_FREELIST_FAIL(fmt, ...) \
-	malloc_zone_check_fail(tiny_freelist_fail_msg, \
-			" (slot=%u), counter=%d\n" fmt, slot, counter, __VA_ARGS__);
-
 boolean_t
-tiny_free_list_check(rack_t *rack, grain_t slot, unsigned counter)
+tiny_free_list_check(szone_t *szone, grain_t slot)
 {
 	mag_index_t mag_index;
 
-	for (mag_index = -1; mag_index < rack->num_magazines; mag_index++) {
-		magazine_t *tiny_mag_ptr = &(rack->magazines[mag_index]);
-		SZONE_MAGAZINE_PTR_LOCK(tiny_mag_ptr);
+	for (mag_index = -1; mag_index < szone->num_tiny_magazines; mag_index++) {
+		magazine_t *tiny_mag_ptr = &(szone->tiny_magazines[mag_index]);
+		SZONE_MAGAZINE_PTR_LOCK(szone, tiny_mag_ptr);
 
 		unsigned count = 0;
-		tiny_free_list_t *ptr = rack->magazines[mag_index].mag_free_list[slot].p;
+		tiny_free_list_t *ptr = szone->tiny_magazines[mag_index].mag_free_list[slot].p;
 		boolean_t is_free;
 		tiny_free_list_t *previous = NULL;
 
 		while (ptr) {
 			is_free = tiny_meta_header_is_free(ptr);
 			if (!is_free) {
-				TINY_FREELIST_FAIL("*** in-use ptr in free list slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+				malloc_printf("*** in-use ptr in free list slot=%d count=%d ptr=%p\n", slot, count, ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				return 0;
 			}
 			if (((uintptr_t)ptr) & (TINY_QUANTUM - 1)) {
-				TINY_FREELIST_FAIL("*** unaligned ptr in free list slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+				malloc_printf("*** unaligned ptr in free list slot=%d  count=%d ptr=%p\n", slot, count, ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				return 0;
 			}
-			if (!tiny_region_for_ptr_no_lock(rack, ptr)) {
-				TINY_FREELIST_FAIL("*** ptr not in szone slot=%d  count=%u ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			if (!tiny_region_for_ptr_no_lock(szone, ptr)) {
+				malloc_printf("*** ptr not in szone slot=%d  count=%d ptr=%p\n", slot, count, ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				return 0;
 			}
-			if (free_list_unchecksum_ptr(rack, &ptr->previous) != previous) {
-				TINY_FREELIST_FAIL("*** previous incorrectly set slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+			if (free_list_unchecksum_ptr(szone, &ptr->previous) != previous) {
+				malloc_printf("*** previous incorrectly set slot=%d  count=%d ptr=%p\n", slot, count, ptr);
+				SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 				return 0;
 			}
 			previous = ptr;
-			ptr = free_list_unchecksum_ptr(rack, &ptr->next);
+			ptr = free_list_unchecksum_ptr(szone, &ptr->next);
 			count++;
 		}
 		
-		SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
+		SZONE_MAGAZINE_PTR_UNLOCK(szone, tiny_mag_ptr);
 	}
 	return 1;
 }
-
-boolean_t
-tiny_check(rack_t *rack, unsigned counter)
-{
-	size_t index;
-
-	/* check tiny regions - chould check region count */
-	for (index = 0; index < rack->region_generation->num_regions_allocated; ++index) {
-		region_t tiny = rack->region_generation->hashed_regions[index];
-
-		if (HASHRING_REGION_DEALLOCATED == tiny) {
-			continue;
-		}
-
-		if (tiny) {
-			magazine_t *tiny_mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-					REGION_TRAILER_FOR_TINY_REGION(tiny),
-					MAGAZINE_INDEX_FOR_TINY_REGION(tiny));
-
-			if (!tiny_check_region(rack, tiny, index, counter)) {
-				SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-				return 0;
-			}
-			SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr);
-		}
-	}
-
-	/* check tiny free lists */
-	for (index = 0; index < NUM_TINY_SLOTS; ++index) {
-		if (!tiny_free_list_check(rack, (grain_t)index, counter)) {
-			return 0;
-		}
-	}
-
-	return 1;
-}