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src/magazine_malloc.c libmalloc-283 libmalloc-166.200.60
--- libmalloc/libmalloc-283/src/magazine_malloc.c
+++ libmalloc/libmalloc-166.200.60/src/magazine_malloc.c
@@ -26,12 +26,10 @@
 /*
  * Multithread enhancements for "tiny" allocations introduced February 2008.
  * These are in the spirit of "Hoard". See:
- * Emery D. Berger, Kathryn S. McKinley, Robert D. Blumofe, and Paul R. Wilson. 2000.
- * Hoard: a scalable memory allocator for multithreaded applications.
- * In Proceedings of the ninth international conference on Architectural support for
- * programming languages and operating systems (ASPLOS IX).
- * ACM, New York, NY, USA, 117-128.
- * DOI: https://doi.org/10.1145/378993.379232
+ * Berger, E.D.; McKinley, K.S.; Blumofe, R.D.; Wilson, P.R. (2000).
+ * "Hoard: a scalable memory allocator for multithreaded applications".
+ * ACM SIGPLAN Notices 35 (11): 117-128. Berger2000.
+ * <http://portal.acm.org/citation.cfm?id=356989.357000>
  * Retrieved on 2008-02-22.
  */
 
@@ -46,20 +44,6 @@
 // Maximum number of magazines, set from the number of logical CPUS and
 // possibly limited by the MallocMaxMagazines environment variable.
 int max_magazines;
-
-// Control whether medium is enabled at all when creating new magazine zones
-bool magazine_medium_enabled = true;
-
-// Control the DRAM limit at which medium kicks in.
-uint64_t magazine_medium_active_threshold = MEDIUM_ACTIVATION_THRESHOLD;
-
-// Control the DRAM limit at which the expanded large cache kicks in.
-uint64_t magazine_large_expanded_cache_threshold = LARGE_CACHE_EXPANDED_THRESHOLD;
-
-// <rdar://problem/47353961> Maximum number of magzines that the medium
-// allocator will use. This addresses a 32-bit load-offset range issue found
-// in some apps when introducing medium.
-int max_medium_magazines;
 
 // Number of regions to retain in a recirc depot.
 #if CONFIG_RECIRC_DEPOT
@@ -96,7 +80,7 @@
 			malloc_zone_error(szone->debug_flags, true, "Pointer %p to metadata being freed\n", ptr);
 			return;
 		}
-		free_tiny(&szone->tiny_rack, ptr, tiny_region, 0, false);
+		free_tiny(&szone->tiny_rack, ptr, tiny_region, 0);
 		return;
 	}
 
@@ -116,20 +100,6 @@
 		return;
 	}
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	region_t medium_region;
-
-	if (szone->is_medium_engaged &&
-			(medium_region = medium_region_for_ptr_no_lock(&szone->medium_rack, ptr)) != NULL) {
-		if (MEDIUM_META_INDEX_FOR_PTR(ptr) >= NUM_MEDIUM_BLOCKS) {
-			malloc_zone_error(szone->debug_flags, true, "Pointer %p to metadata being freed (2)\n", ptr);
-			return;
-		}
-		free_medium(&szone->medium_rack, ptr, medium_region, 0);
-		return;
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 	/* check that it's a legal large allocation */
 	if ((uintptr_t)ptr & (vm_page_quanta_size - 1)) {
 		malloc_zone_error(szone->debug_flags, true, "non-page-aligned, non-allocated pointer %p being freed\n", ptr);
@@ -163,12 +133,12 @@
 		malloc_zone_error(szone->debug_flags, true, "Non-aligned pointer %p being freed\n", ptr);
 		return;
 	}
-	if (size <= TINY_LIMIT_THRESHOLD) {
+	if (size <= SMALL_THRESHOLD) {
 		if (TINY_INDEX_FOR_PTR(ptr) >= NUM_TINY_BLOCKS) {
 			malloc_zone_error(szone->debug_flags, true, "Pointer %p to metadata being freed\n", ptr);
 			return;
 		}
-		free_tiny(&szone->tiny_rack, ptr, TINY_REGION_FOR_PTR(ptr), size, false);
+		free_tiny(&szone->tiny_rack, ptr, TINY_REGION_FOR_PTR(ptr), size);
 		return;
 	}
 
@@ -179,7 +149,7 @@
 		malloc_zone_error(szone->debug_flags, true, "Non-aligned pointer %p being freed (2)\n", ptr);
 		return;
 	}
-	if (size <= SMALL_LIMIT_THRESHOLD) {
+	if (size <= szone->large_threshold) {
 		if (SMALL_META_INDEX_FOR_PTR(ptr) >= NUM_SMALL_BLOCKS) {
 			malloc_zone_error(szone->debug_flags, true, "Pointer %p to metadata being freed (2)\n", ptr);
 			return;
@@ -187,20 +157,6 @@
 		free_small(&szone->small_rack, ptr, SMALL_REGION_FOR_PTR(ptr), size);
 		return;
 	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	/*
-	 * Try to free to a medium region.
-	 */
-	if (szone->is_medium_engaged && size <= MEDIUM_LIMIT_THRESHOLD) {
-		if (MEDIUM_META_INDEX_FOR_PTR(ptr) >= NUM_MEDIUM_BLOCKS) {
-			malloc_zone_error(szone->debug_flags, true, "Pointer %p to metadata being freed (2)\n", ptr);
-			return;
-		}
-		free_medium(&szone->medium_rack, ptr, MEDIUM_REGION_FOR_PTR(ptr), size);
-		return;
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	/* check that it's a legal large allocation */
 	if ((uintptr_t)ptr & (vm_page_quanta_size - 1)) {
@@ -216,27 +172,24 @@
 	void *ptr;
 	msize_t msize;
 
-	if (size <= TINY_LIMIT_THRESHOLD) {
+	if (size <= SMALL_THRESHOLD) {
+		// tiny size: <=1008 bytes (64-bit), <=496 bytes (32-bit)
+		// think tiny
 		msize = TINY_MSIZE_FOR_BYTES(size + TINY_QUANTUM - 1);
 		if (!msize) {
 			msize = 1;
 		}
 		ptr = tiny_malloc_should_clear(&szone->tiny_rack, msize, cleared_requested);
-	} else if (size <= SMALL_LIMIT_THRESHOLD) {
+	} else if (size <= szone->large_threshold) {
+		// small size: <=15k (iOS), <=64k (large iOS), <=128k (macOS)
+		// think small
 		msize = SMALL_MSIZE_FOR_BYTES(size + SMALL_QUANTUM - 1);
 		if (!msize) {
 			msize = 1;
 		}
 		ptr = small_malloc_should_clear(&szone->small_rack, msize, cleared_requested);
-#if CONFIG_MEDIUM_ALLOCATOR
-	} else if (szone->is_medium_engaged && size <= MEDIUM_LIMIT_THRESHOLD) {
-		msize = MEDIUM_MSIZE_FOR_BYTES(size + MEDIUM_QUANTUM - 1);
-		if (!msize) {
-			msize = 1;
-		}
-		ptr = medium_malloc_should_clear(&szone->medium_rack, msize, cleared_requested);
-#endif
 	} else {
+		// large: all other allocations
 		size_t num_kernel_pages = round_page_quanta(size) >> vm_page_quanta_shift;
 		if (num_kernel_pages == 0) { /* Overflowed */
 			ptr = 0;
@@ -280,7 +233,7 @@
 {
 	void *ptr;
 
-	if (size <= MEDIUM_LIMIT_THRESHOLD) {
+	if (size <= szone->large_threshold) {
 		ptr = szone_memalign(szone, vm_page_quanta_size, size);
 	} else {
 		size_t num_kernel_pages;
@@ -355,18 +308,6 @@
 	if (sz) {
 		return sz;
 	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	/*
-	 * Look for it in a medium region.
-	 */
-	if (szone->is_medium_engaged) {
-		sz = medium_size(&szone->medium_rack, ptr);
-		if (sz) {
-			return sz;
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	/*
 	 * If not page-aligned, it cannot have come from a large allocation.
@@ -418,8 +359,8 @@
 	 * If the new size suits the tiny allocator and the pointer being resized
 	 * belongs to a tiny region, try to reallocate in-place.
 	 */
-	if (new_good_size <= TINY_LIMIT_THRESHOLD) {
-		if (old_size <= TINY_LIMIT_THRESHOLD) {
+	if (new_good_size <= SMALL_THRESHOLD) {
+		if (old_size <= SMALL_THRESHOLD) {
 			if (new_good_size <= (old_size >> 1)) {
 				/*
 				 * Serious shrinkage (more than half). free() the excess.
@@ -447,8 +388,8 @@
 		 * belongs to a small region, and we're not protecting the small allocations
 		 * try to reallocate in-place.
 		 */
-	} else if (new_good_size <= SMALL_LIMIT_THRESHOLD) {
-		if (TINY_LIMIT_THRESHOLD < old_size && old_size <= SMALL_LIMIT_THRESHOLD) {
+	} else if (new_good_size <= szone->large_threshold) {
+		if (SMALL_THRESHOLD < old_size && old_size <= szone->large_threshold) {
 			if (new_good_size <= (old_size >> 1)) {
 				return small_try_shrink_in_place(&szone->small_rack, ptr, old_size, new_good_size);
 			} else if (new_good_size <= old_size) {
@@ -463,30 +404,11 @@
 				return ptr;
 			}
 		}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	} else if (szone->is_medium_engaged && new_good_size <= MEDIUM_LIMIT_THRESHOLD) {
-		if (SMALL_LIMIT_THRESHOLD < old_size && old_size <= MEDIUM_LIMIT_THRESHOLD) {
-			if (new_good_size <= (old_size >> 1)) {
-				return medium_try_shrink_in_place(&szone->medium_rack, ptr, old_size, new_good_size);
-			} else if (new_good_size <= old_size) {
-				if (szone->debug_flags & MALLOC_DO_SCRIBBLE) {
-					memset(ptr + new_size, SCRIBBLE_BYTE, old_size - new_size);
-				}
-			} else if (medium_try_realloc_in_place(&szone->medium_rack, ptr, old_size, new_good_size)) {
-				if (szone->debug_flags & MALLOC_DO_SCRIBBLE) {
-					memset(ptr + old_size, SCRIBBLE_BYTE, new_good_size - old_size);
-				}
-				return ptr;
-			}
-		}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 		/*
 		 * Else if the allocation's a large allocation, try to reallocate in-place there.
 		 */
 	} else if (!(szone->debug_flags & MALLOC_PURGEABLE) && // purgeable needs fresh allocation
-			   (old_size > LARGE_THRESHOLD(szone)) && (new_good_size > LARGE_THRESHOLD(szone))) {
+			   (old_size > szone->large_threshold) && (new_good_size > szone->large_threshold)) {
 		if (new_good_size <= (old_size >> 1)) {
 			return large_try_shrink_in_place(szone, ptr, old_size, new_good_size);
 		} else if (new_good_size <= old_size) {
@@ -524,11 +446,8 @@
 	 * if it's too small, just copy by hand.
 	 */
 	valid_size = MIN(old_size, new_size);
-#if CONFIG_REALLOC_CAN_USE_VMCOPY
-	if ((valid_size <= VM_COPY_THRESHOLD) ||
-			vm_copy(mach_task_self(), (vm_address_t)ptr, valid_size, (vm_address_t)new_ptr))
-#endif
-	{
+	if ((valid_size <= szone->vm_copy_threshold) ||
+			vm_copy(mach_task_self(), (vm_address_t)ptr, valid_size, (vm_address_t)new_ptr)) {
 		memcpy(new_ptr, ptr, valid_size);
 	}
 	szone_free(szone, ptr);
@@ -551,49 +470,32 @@
 		return NULL;
 	}
 
-	// alignment is a power of 2 at least as large as sizeof(void *), hence
-	// non-zero.  Since size + alignment didn't wrap, 0 <= size + alignment - 1
-	// < size + alignment
+	// alignment is gauranteed a power of 2 at least as large as sizeof(void *), hence non-zero.
+	// Since size + alignment didn't wrap, 0 <= size + alignment - 1 < size + alignment
 	size_t span = size + alignment - 1;
 
 	if (alignment <= TINY_QUANTUM) {
-		// Trivially satisfied by tiny, small, medium, or large.
-		return szone_malloc(szone, size);
-	}
-	if (span <= TINY_LIMIT_THRESHOLD) {
+		return szone_malloc(szone, size); // Trivially satisfied by tiny, small, or large
+	}
+	if (span <= SMALL_THRESHOLD) {
 		return tiny_memalign(szone, alignment, size, span);
 	}
-	if (TINY_LIMIT_THRESHOLD < size && alignment <= SMALL_QUANTUM) {
-		// Trivially satisfied by small, medium or large.
-		return szone_malloc(szone, size);
-	}
-	if (size <= TINY_LIMIT_THRESHOLD) {
-		// The allocation asked for a size that TINY would normally fulfill
-		// but it cannot guarantee the alignment. So bump it up to fit inside
-		// SMALL and try again.
-		size = TINY_LIMIT_THRESHOLD + TINY_QUANTUM;
+	if (SMALL_THRESHOLD < size && alignment <= SMALL_QUANTUM) {
+		return szone_malloc(szone, size); // Trivially satisfied by small or large
+	}
+	if (size <= SMALL_THRESHOLD) {
+		// ensure block allocated by small does not have a tiny-possible size
+		size = SMALL_THRESHOLD + TINY_QUANTUM;
 		span = size + alignment - 1;
 	}
-	if (span <= SMALL_LIMIT_THRESHOLD) {
+	if (span <= szone->large_threshold) {
 		return small_memalign(szone, alignment, size, span);
 	}
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		if (size <= SMALL_LIMIT_THRESHOLD) {
-			size = SMALL_LIMIT_THRESHOLD + SMALL_QUANTUM;
-			span = size + alignment - 1;
-		}
-		if (szone->is_medium_engaged && span <= MEDIUM_LIMIT_THRESHOLD) {
-			return medium_memalign(szone, alignment, size, span);
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-	if (LARGE_THRESHOLD(szone) < size && alignment <= vm_page_quanta_size) {
-		// Trivially satisfied by large (which rounds to a whole page).
-		return szone_malloc(szone, size);
+	if (szone->large_threshold < size && alignment <= vm_page_quanta_size) {
+		return szone_malloc(szone, size); // Trivially satisfied by large
 	}
 	// ensure block allocated by large does not have a small-possible size
-	size_t num_kernel_pages = round_page_quanta(MAX(LARGE_THRESHOLD(szone) + 1,
+	size_t num_kernel_pages = round_page_quanta(MAX(szone->large_threshold + 1,
 			size)) >> vm_page_quanta_shift;
 	if (num_kernel_pages == 0) { /* Overflowed */
 		return NULL;
@@ -602,7 +504,6 @@
 				MAX(vm_page_quanta_shift, __builtin_ctz((unsigned)alignment)), 0);
 	}
 	/* NOTREACHED */
-	__builtin_unreachable();
 }
 
 // Given a size, returns the number of pointers allocated capable of holding
@@ -615,7 +516,7 @@
 szone_batch_malloc(szone_t *szone, size_t size, void **results, unsigned count)
 {
 	// only bother implementing this for tiny
-	if (size <= TINY_LIMIT_THRESHOLD) {
+	if (size <= SMALL_THRESHOLD) {
 		return tiny_batch_malloc(szone, size, results, count);
 	}
 	return 0;
@@ -635,7 +536,7 @@
 	// We only support batch malloc in tiny. Let it free all of the pointers
 	// that belong to it, then let the standard free deal with the rest.
 	tiny_batch_free(szone, to_be_freed, count);
-
+	
 	CHECK(szone, __PRETTY_FUNCTION__);
 	while (count--) {
 		void *ptr = to_be_freed[count];
@@ -661,7 +562,7 @@
 
 	// stack allocated copy of the death-row cache
 	int idx = szone->large_entry_cache_oldest, idx_max = szone->large_entry_cache_newest;
-	large_entry_t local_entry_cache[LARGE_ENTRY_CACHE_SIZE_HIGH];
+	large_entry_t local_entry_cache[LARGE_ENTRY_CACHE_SIZE];
 
 	memcpy((void *)local_entry_cache, (void *)szone->large_entry_cache, sizeof(local_entry_cache));
 
@@ -676,7 +577,7 @@
 	// deallocate the death-row cache outside the zone lock
 	while (idx != idx_max) {
 		mvm_deallocate_pages((void *)local_entry_cache[idx].address, local_entry_cache[idx].size, 0);
-		if (++idx == szone->large_cache_depth) {
+		if (++idx == LARGE_ENTRY_CACHE_SIZE) {
 			idx = 0;
 		}
 	}
@@ -707,13 +608,6 @@
 	rack_destroy(&szone->tiny_rack);
 	rack_destroy(&szone->small_rack);
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		rack_destroy_regions(&szone->medium_rack, MEDIUM_REGION_SIZE);
-		rack_destroy(&szone->medium_rack);
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 	mvm_deallocate_pages((void *)szone, SZONE_PAGED_SIZE, 0);
 }
 
@@ -723,7 +617,7 @@
 	msize_t msize;
 
 	// Find a good size for this tiny allocation.
-	if (size <= TINY_LIMIT_THRESHOLD) {
+	if (size <= SMALL_THRESHOLD) {
 		msize = TINY_MSIZE_FOR_BYTES(size + TINY_QUANTUM - 1);
 		if (!msize) {
 			msize = 1;
@@ -732,23 +626,13 @@
 	}
 
 	// Find a good size for this small allocation.
-	if (size <= SMALL_LIMIT_THRESHOLD) {
+	if (size <= szone->large_threshold) {
 		msize = SMALL_MSIZE_FOR_BYTES(size + SMALL_QUANTUM - 1);
 		if (!msize) {
 			msize = 1;
 		}
 		return SMALL_BYTES_FOR_MSIZE(msize);
 	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged && size <= MEDIUM_LIMIT_THRESHOLD) {
-		msize = MEDIUM_MSIZE_FOR_BYTES(size + MEDIUM_QUANTUM - 1);
-		if (!msize) {
-			msize = 1;
-		}
-		return MEDIUM_BYTES_FOR_MSIZE(msize);
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	// Check for integer overflow on the size, since unlike the two cases above,
 	// there is no upper bound on allocation size at this point.
@@ -772,10 +656,6 @@
 {
 	return tiny_claimed_address(&szone->tiny_rack, ptr)
 			|| small_claimed_address(&szone->small_rack, ptr)
-#if CONFIG_MEDIUM_ALLOCATOR
-			|| (szone->is_medium_engaged &&
-					medium_claimed_address(&szone->medium_rack, ptr))
-#endif // CONFIG_MEDIUM_ALLOCATOR
 			|| large_claimed_address(szone, ptr);
 }
 
@@ -845,39 +725,6 @@
 			return 0;
 		}
 	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		/* check medium regions - could check region count */
-		for (index = 0; index < szone->medium_rack.region_generation->num_regions_allocated; ++index) {
-			region_t medium = szone->medium_rack.region_generation->hashed_regions[index];
-
-			if (HASHRING_REGION_DEALLOCATED == medium) {
-				continue;
-			}
-
-			if (medium) {
-				magazine_t *medium_mag_ptr = mag_lock_zine_for_region_trailer(szone->medium_rack.magazines,
-						REGION_TRAILER_FOR_MEDIUM_REGION(medium),
-						MAGAZINE_INDEX_FOR_MEDIUM_REGION(medium));
-
-				if (!medium_check_region(&szone->medium_rack, medium, index, szone_check_counter)) {
-					SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-					szone->debug_flags &= ~CHECK_REGIONS;
-					return 0;
-				}
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			}
-		}
-		/* check medium free lists */
-		for (index = 0; index < MEDIUM_FREE_SLOT_COUNT(&szone->medium_rack); ++index) {
-			if (!medium_free_list_check(&szone->medium_rack, (grain_t)index, szone_check_counter)) {
-				szone->debug_flags &= ~CHECK_REGIONS;
-				return 0;
-			}
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	return 1;
 }
@@ -912,7 +759,7 @@
 	kern_return_t err;
 
 	if (!reader) {
-		reader = _malloc_default_reader;
+		reader = _szone_default_reader;
 	}
 
 	err = reader(task, zone_address, sizeof(szone_t), (void **)&szone);
@@ -930,23 +777,14 @@
 		return err;
 	}
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		err = medium_in_use_enumerator(task, context, type_mask, szone, reader, recorder);
-		if (err) {
-			return err;
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 	err = large_in_use_enumerator(
 			task, context, type_mask, (vm_address_t)szone->large_entries, szone->num_large_entries, reader, recorder);
 	return err;
 }
 
-static boolean_t
-scalable_zone_info_task(task_t task, memory_reader_t reader,
-		malloc_zone_t *zone, unsigned *info_to_fill, unsigned count)
+// Following method is deprecated:  use scalable_zone_statistics instead
+void
+scalable_zone_info(malloc_zone_t *zone, unsigned *info_to_fill, unsigned count)
 {
 	szone_t *szone = (void *)zone;
 	unsigned info[13];
@@ -958,30 +796,21 @@
 	size_t u = 0;
 	mag_index_t mag_index;
 
-	magazine_t *mapped_magazines;
-	if (reader(task, (vm_address_t)szone->tiny_rack.magazines,
-			sizeof(magazine_t), (void **)&mapped_magazines)) {
-		return false;
-	}
 	for (mag_index = -1; mag_index < szone->tiny_rack.num_magazines; mag_index++) {
-		s += mapped_magazines[mag_index].mag_bytes_free_at_start;
-		s += mapped_magazines[mag_index].mag_bytes_free_at_end;
-		t += mapped_magazines[mag_index].mag_num_objects;
-		u += mapped_magazines[mag_index].mag_num_bytes_in_objects;
+		s += szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_start;
+		s += szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_end;
+		t += szone->tiny_rack.magazines[mag_index].mag_num_objects;
+		u += szone->tiny_rack.magazines[mag_index].mag_num_bytes_in_objects;
 	}
 
 	info[4] = (unsigned)t;
 	info[5] = (unsigned)u;
 
-	if (reader(task, (vm_address_t)szone->small_rack.magazines,
-			sizeof(magazine_t), (void **)&mapped_magazines)) {
-		return false;
-	}
 	for (t = 0, u = 0, mag_index = -1; mag_index < szone->small_rack.num_magazines; mag_index++) {
-		s += mapped_magazines[mag_index].mag_bytes_free_at_start;
-		s += mapped_magazines[mag_index].mag_bytes_free_at_end;
-		t += mapped_magazines[mag_index].mag_num_objects;
-		u += mapped_magazines[mag_index].mag_num_bytes_in_objects;
+		s += szone->small_rack.magazines[mag_index].mag_bytes_free_at_start;
+		s += szone->small_rack.magazines[mag_index].mag_bytes_free_at_end;
+		t += szone->small_rack.magazines[mag_index].mag_num_objects;
+		u += szone->small_rack.magazines[mag_index].mag_num_bytes_in_objects;
 	}
 
 	info[6] = (unsigned)t;
@@ -1003,266 +832,64 @@
 
 	info[2] = info[3] - (unsigned)s;
 	memcpy(info_to_fill, info, sizeof(unsigned) * count);
-
-	return true;
-}
-
-// Following method is deprecated:  use scalable_zone_statistics instead
-// Required for backward compatibility.
-void
-scalable_zone_info(malloc_zone_t *zone, unsigned *info_to_fill, unsigned count) {
-	scalable_zone_info_task(mach_task_self(), _malloc_default_reader, zone,
-			info_to_fill, count);
 }
 
 // FIXME: consistent picture requires locking!
 static MALLOC_NOINLINE void
-szone_print(task_t task, unsigned level, vm_address_t zone_address,
-		memory_reader_t reader, print_task_printer_t printer)
+szone_print(szone_t *szone, boolean_t verbose)
 {
 	unsigned info[13];
 	size_t index;
 	region_t region;
-	region_t mapped_region;
-
-	szone_t *szone = (szone_t *)zone_address;
-	szone_t *mapped_szone;
-	if (reader(task, zone_address, sizeof(szone_t), (void **)&mapped_szone)) {
-		printer("Failed to read szone structure\n");
-		return;
-	}
-
-	if (!scalable_zone_info_task(task, reader, (void *)mapped_szone, info, 13)) {
-		printer("Failed to get scalable zone info\n");
-		return;
-	}
-	printer("Scalable zone %p: inUse=%u(%u) touched=%u allocated=%u flags=0x%x\n",
-			zone_address, info[0], info[1], info[2], info[3], info[12]);
-	printer("\ttiny=%u(%u) small=%u(%u) large=%u(%u)\n", info[4],
-			info[5], info[6], info[7], info[8], info[9]);
+
+	scalable_zone_info((void *)szone, info, 13);
+	malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX,
+			"Scalable zone %p: inUse=%u(%y) touched=%y allocated=%y flags=%d\n", szone, info[0], info[1], info[2], info[3],
+			info[12]);
+	malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "\ttiny=%u(%y) small=%u(%y) large=%u(%y) huge=%u(%y)\n", info[4],
+			info[5], info[6], info[7], info[8], info[9], info[10], info[11]);
 	// tiny
-	printer("%lu tiny regions:\n", mapped_szone->tiny_rack.num_regions);
-	if (mapped_szone->tiny_rack.num_regions_dealloc) {
-		printer("[%lu tiny regions have been vm_deallocate'd]\n",
-				mapped_szone->tiny_rack.num_regions_dealloc);
-	}
-
-	region_hash_generation_t *mapped_region_generation;
-	region_t *mapped_hashed_regions;
-	magazine_t *mapped_magazines;
-	if (reader(task, (vm_address_t)mapped_szone->tiny_rack.region_generation,
-			sizeof(region_hash_generation_t), (void **)&mapped_region_generation)) {
-		printer("Failed to map tiny rack region_generation\n");
-		return;
-	}
-	if (reader(task, (vm_address_t)mapped_region_generation->hashed_regions,
-			sizeof(region_t), (void **)&mapped_hashed_regions)) {
-		printer("Failed to map tiny rack hashed_regions\n");
-		return;
-	}
-	if (reader(task, (vm_address_t)mapped_szone->tiny_rack.magazines,
-			mapped_szone->tiny_rack.num_magazines * sizeof(magazine_t),
-			(void **)&mapped_magazines)) {
-		printer("Failed to map tiny rack magazines\n");
-		return;
-	}
-
-	int recirc_regions = 0;
-	for (index = 0; index < mapped_region_generation->num_regions_allocated; ++index) {
-		region = mapped_hashed_regions[index];
+	malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "%lu tiny regions:\n", szone->tiny_rack.num_regions);
+	if (szone->tiny_rack.num_regions_dealloc) {
+		malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "[%lu tiny regions have been vm_deallocate'd]\n",
+				szone->tiny_rack.num_regions_dealloc);
+	}
+	for (index = 0; index < szone->tiny_rack.region_generation->num_regions_allocated; ++index) {
+		region = szone->tiny_rack.region_generation->hashed_regions[index];
 		if (HASHRING_OPEN_ENTRY != region && HASHRING_REGION_DEALLOCATED != region) {
-			if (reader(task, (vm_address_t)region, sizeof(struct tiny_region),
-					(void **)&mapped_region)) {
-				printer("Failed to map region %p\n", region);
-				return;
-			}
-			mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(mapped_region);
-			if (mag_index == DEPOT_MAGAZINE_INDEX) {
-				recirc_regions++;
-			}
-			print_tiny_region(task, reader, printer, level, region,
-					(region == mapped_magazines[mag_index].mag_last_region)
-						? mapped_magazines[mag_index].mag_bytes_free_at_start
-						: 0,
-					(region == mapped_magazines[mag_index].mag_last_region)
-						? mapped_magazines[mag_index].mag_bytes_free_at_end
-						: 0);
-		}
-	}
-
-#if CONFIG_RECIRC_DEPOT
-	magazine_t *mapped_recirc_depot = &mapped_magazines[DEPOT_MAGAZINE_INDEX];
-	if (mapped_recirc_depot->mag_num_bytes_in_objects) {
-		printer("Tiny recirc depot: total bytes: %llu, in-use bytes: %llu, "
-				"allocations: %llu, regions: %d (min # retained regions: %d)\n",
-				mapped_recirc_depot->num_bytes_in_magazine,
-				mapped_recirc_depot->mag_num_bytes_in_objects,
-				mapped_recirc_depot->mag_num_objects, recirc_regions,
-				recirc_retained_regions);
-	} else {
-		printer("Tiny recirc depot is empty\n");
-	}
-#else // CONFIG_RECIRC_DEPOT
-	printer("Tiny recirc depot not configured\n");
-#endif // CONFIG_RECIRC_DEPOT
-
-	if (level > 0) {
-		print_tiny_free_list(task, reader, printer, &szone->tiny_rack);
-	}
-
+			mag_index_t mag_index = MAGAZINE_INDEX_FOR_TINY_REGION(region);
+			print_tiny_region(verbose, region, (region == szone->tiny_rack.magazines[mag_index].mag_last_region)
+													   ? szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_start
+													   : 0,
+					(region == szone->tiny_rack.magazines[mag_index].mag_last_region)
+							? szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_end
+							: 0);
+		}
+	}
+	if (verbose) {
+		print_tiny_free_list(&szone->tiny_rack);
+	}
 	// small
-	printer("%lu small regions:\n", mapped_szone->small_rack.num_regions);
-	if (mapped_szone->small_rack.num_regions_dealloc) {
-		printer("[%lu small regions have been vm_deallocate'd]\n",
-				mapped_szone->small_rack.num_regions_dealloc);
-	}
-	if (reader(task, (vm_address_t)mapped_szone->small_rack.region_generation,
-			sizeof(region_hash_generation_t), (void **)&mapped_region_generation)) {
-		printer("Failed to map small rack region_generation\n");
-		return;
-	}
-	if (reader(task, (vm_address_t)mapped_region_generation->hashed_regions,
-			sizeof(region_t), (void **)&mapped_hashed_regions)) {
-		printer("Failed to map small rack hashed_regions\n");
-		return;
-	}
-	if (reader(task, (vm_address_t)mapped_szone->small_rack.magazines,
-			mapped_szone->small_rack.num_magazines * sizeof(magazine_t),
-			(void **)&mapped_magazines)) {
-		printer("Failed to map small rack magazines\n");
-		return;
-	}
-
-	recirc_regions = 0;
-	for (index = 0; index < mapped_region_generation->num_regions_allocated; ++index) {
-		region = mapped_hashed_regions[index];
+	malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "%lu small regions:\n", szone->small_rack.num_regions);
+	if (szone->small_rack.num_regions_dealloc) {
+		malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "[%lu small regions have been vm_deallocate'd]\n",
+				szone->small_rack.num_regions_dealloc);
+	}
+	for (index = 0; index < szone->small_rack.region_generation->num_regions_allocated; ++index) {
+		region = szone->small_rack.region_generation->hashed_regions[index];
 		if (HASHRING_OPEN_ENTRY != region && HASHRING_REGION_DEALLOCATED != region) {
-			if (reader(task, (vm_address_t)region, sizeof(struct small_region),
-					(void **)&mapped_region)) {
-				printer("Failed to map region %p\n", region);
-				return;
-			}
-			mag_index_t mag_index = MAGAZINE_INDEX_FOR_SMALL_REGION(mapped_region);
-			if (mag_index == DEPOT_MAGAZINE_INDEX) {
-				recirc_regions++;
-			}
-			print_small_region(task, reader, printer, mapped_szone, level, region,
-					(region == mapped_magazines[mag_index].mag_last_region)
-						? mapped_magazines[mag_index].mag_bytes_free_at_start
-						: 0,
-					(region == mapped_magazines[mag_index].mag_last_region)
-						? mapped_magazines[mag_index].mag_bytes_free_at_end
-						: 0);
-		}
-	}
-
-#if CONFIG_RECIRC_DEPOT
-	mapped_recirc_depot = &mapped_magazines[DEPOT_MAGAZINE_INDEX];
-	if (mapped_recirc_depot->mag_num_bytes_in_objects) {
-		printer("Small recirc depot: total bytes: %llu, in-use bytes: %llu, "
-				"allocations: %llu, regions: %d (min # retained regions: %d)\n",
-				mapped_recirc_depot->num_bytes_in_magazine,
-				mapped_recirc_depot->mag_num_bytes_in_objects,
-				mapped_recirc_depot->mag_num_objects, recirc_regions,
-				recirc_retained_regions);
-	} else {
-		printer("Small recirc depot is empty\n");
-	}
-#else // CONFIG_RECIRC_DEPOT
-	printer("Small recirc depot not configured\n");
-#endif // CONFIG_RECIRC_DEPOT
-
-	if (level > 0) {
-		print_small_free_list(task, reader, printer, &szone->small_rack);
-	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		// medium
-		printer("%lu medium regions:\n", mapped_szone->medium_rack.num_regions);
-		if (mapped_szone->medium_rack.num_regions_dealloc) {
-			printer("[%lu medium regions have been vm_deallocate'd]\n",
-					mapped_szone->medium_rack.num_regions_dealloc);
-		}
-		if (reader(task, (vm_address_t)mapped_szone->medium_rack.region_generation,
-				sizeof(region_hash_generation_t), (void **)&mapped_region_generation)) {
-			printer("Failed to map medium rack region_generation\n");
-			return;
-		}
-		if (reader(task, (vm_address_t)mapped_region_generation->hashed_regions,
-				sizeof(region_t), (void **)&mapped_hashed_regions)) {
-			printer("Failed to map medium rack hashed_regions\n");
-			return;
-		}
-		if (reader(task, (vm_address_t)mapped_szone->medium_rack.magazines,
-				mapped_szone->medium_rack.num_magazines * sizeof(magazine_t),
-				(void **)&mapped_magazines)) {
-			printer("Failed to map medium rack magazines\n");
-			return;
-		}
-
-		recirc_regions = 0;
-		for (index = 0; index < mapped_region_generation->num_regions_allocated; ++index) {
-			region = mapped_hashed_regions[index];
-			if (HASHRING_OPEN_ENTRY != region && HASHRING_REGION_DEALLOCATED != region) {
-				if (reader(task, (vm_address_t)region, sizeof(struct medium_region),
-						(void **)&mapped_region)) {
-					printer("Failed to map region %p\n", region);
-					return;
-				}
-				mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(mapped_region);
-				if (mag_index == DEPOT_MAGAZINE_INDEX) {
-					recirc_regions++;
-				}
-				print_medium_region(task, reader, printer, mapped_szone, level,
-						region,
-						(region == mapped_magazines[mag_index].mag_last_region)
-							? mapped_magazines[mag_index].mag_bytes_free_at_start
-							: 0,
-						(region == mapped_magazines[mag_index].mag_last_region)
-							? mapped_magazines[mag_index].mag_bytes_free_at_end
+			mag_index_t mag_index = MAGAZINE_INDEX_FOR_SMALL_REGION(region);
+			print_small_region(szone, verbose, region, (region == szone->small_rack.magazines[mag_index].mag_last_region)
+															   ? szone->small_rack.magazines[mag_index].mag_bytes_free_at_start
+															   : 0,
+					(region == szone->small_rack.magazines[mag_index].mag_last_region)
+							? szone->small_rack.magazines[mag_index].mag_bytes_free_at_end
 							: 0);
-			}
-		}
-
-#if CONFIG_RECIRC_DEPOT
-		mapped_recirc_depot = &mapped_magazines[DEPOT_MAGAZINE_INDEX];
-		if (mapped_recirc_depot->mag_num_bytes_in_objects) {
-			printer("Medium recirc depot: total bytes: %llu, in-use bytes: %llu, "
-					"allocations: %llu, regions: %d (min # retained regions: %d)\n",
-					mapped_recirc_depot->num_bytes_in_magazine,
-					mapped_recirc_depot->mag_num_bytes_in_objects,
-					mapped_recirc_depot->mag_num_objects, recirc_regions,
-					recirc_retained_regions);
-		} else {
-			printer("Medium recirc depot is empty\n");
-		}
-#else // CONFIG_RECIRC_DEPOT
-		printer("Medium recirc depot not configured\n");
-#endif // CONFIG_RECIRC_DEPOT
-
-		if (level > 0) {
-			print_medium_free_list(task, reader, printer, &szone->medium_rack);
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
-	// Large
-	large_debug_print(task, level, zone_address, reader, printer);
-}
-
-static void
-szone_print_self(szone_t *szone, boolean_t verbose)
-{
-	szone_print(mach_task_self(), verbose ? MALLOC_VERBOSE_PRINT_LEVEL : 0,
-			(vm_address_t)szone, _malloc_default_reader, malloc_report_simple);
-}
-
-static void
-szone_print_task(task_t task, unsigned level, vm_address_t zone_address,
-		memory_reader_t reader, print_task_printer_t printer)
-{
-	szone_print(task, level, zone_address, reader, printer);
+		}
+	}
+	if (verbose) {
+		print_small_free_list(&szone->small_rack);
+	}
 }
 
 static void
@@ -1304,15 +931,6 @@
 	}
 	szone_force_lock_magazine(szone, &szone->small_rack.magazines[DEPOT_MAGAZINE_INDEX]);
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		for (i = 0; i < szone->medium_rack.num_magazines; ++i) {
-			szone_force_lock_magazine(szone, &szone->medium_rack.magazines[i]);
-		}
-		szone_force_lock_magazine(szone, &szone->medium_rack.magazines[DEPOT_MAGAZINE_INDEX]);
-	}
-#endif
-
 	SZONE_LOCK(szone);
 }
 
@@ -1323,14 +941,6 @@
 
 	SZONE_UNLOCK(szone);
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		for (i = -1; i < szone->medium_rack.num_magazines; ++i) {
-			SZONE_MAGAZINE_PTR_UNLOCK((&(szone->medium_rack.magazines[i])));
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 	for (i = -1; i < szone->small_rack.num_magazines; ++i) {
 		SZONE_MAGAZINE_PTR_UNLOCK((&(szone->small_rack.magazines[i])));
 	}
@@ -1346,14 +956,6 @@
 	mag_index_t i;
 
 	SZONE_REINIT_LOCK(szone);
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		for (i = -1; i < szone->medium_rack.num_magazines; ++i) {
-			SZONE_MAGAZINE_PTR_REINIT_LOCK((&(szone->medium_rack.magazines[i])));
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	for (i = -1; i < szone->small_rack.num_magazines; ++i) {
 		SZONE_MAGAZINE_PTR_REINIT_LOCK((&(szone->small_rack.magazines[i])));
@@ -1375,18 +977,6 @@
 		return 1;
 	}
 	SZONE_UNLOCK(szone);
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		for (i = -1; i < szone->small_rack.num_magazines; ++i) {
-				tookLock = SZONE_MAGAZINE_PTR_TRY_LOCK((&(szone->small_rack.magazines[i])));
-				if (tookLock == 0) {
-					return 1;
-				}
-				SZONE_MAGAZINE_PTR_UNLOCK((&(szone->small_rack.magazines[i])));
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
 
 	for (i = -1; i < szone->small_rack.num_magazines; ++i) {
 		tookLock = SZONE_MAGAZINE_PTR_TRY_LOCK((&(szone->small_rack.magazines[i])));
@@ -1415,15 +1005,159 @@
 	MALLOC_TRACE(TRACE_malloc_memory_pressure | DBG_FUNC_START, (uint64_t)szone, goal, 0, 0);
 
 #if CONFIG_MADVISE_PRESSURE_RELIEF
-	tiny_madvise_pressure_relief(&szone->tiny_rack);
-	small_madvise_pressure_relief(&szone->small_rack);
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		medium_madvise_pressure_relief(&szone->medium_rack);
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-#endif // CONFIG_MADVISE_PRESSURE_RELIEF
+	mag_index_t mag_index;
+
+	magazine_t *tiny_depot_ptr = (&szone->tiny_rack.magazines[DEPOT_MAGAZINE_INDEX]);
+	magazine_t *small_depot_ptr = (&szone->small_rack.magazines[DEPOT_MAGAZINE_INDEX]);
+
+	for (mag_index = 0; mag_index < szone->tiny_rack.num_magazines; mag_index++) {
+		size_t index;
+		for (index = 0; index < szone->tiny_rack.region_generation->num_regions_allocated; ++index) {
+			SZONE_LOCK(szone);
+
+			region_t tiny = szone->tiny_rack.region_generation->hashed_regions[index];
+			if (!tiny || tiny == HASHRING_REGION_DEALLOCATED) {
+				SZONE_UNLOCK(szone);
+				continue;
+			}
+
+			magazine_t *mag_ptr = mag_lock_zine_for_region_trailer(szone->tiny_rack.magazines,
+					REGION_TRAILER_FOR_TINY_REGION(tiny),
+					MAGAZINE_INDEX_FOR_TINY_REGION(tiny));
+			SZONE_UNLOCK(szone);
+
+			/* 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 (tiny == mag_ptr->mag_last_region && (mag_ptr->mag_bytes_free_at_end || mag_ptr->mag_bytes_free_at_start)) {
+				tiny_finalize_region(&szone->tiny_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(&szone->tiny_rack, mag_ptr, REGION_TRAILER_FOR_TINY_REGION(tiny));
+			int objects_in_use = tiny_free_detach_region(&szone->tiny_rack, mag_ptr, tiny);
+
+			SZONE_MAGAZINE_PTR_LOCK(tiny_depot_ptr);
+			MAGAZINE_INDEX_FOR_TINY_REGION(tiny) = DEPOT_MAGAZINE_INDEX;
+			REGION_TRAILER_FOR_TINY_REGION(tiny)->pinned_to_depot = 0;
+
+			size_t bytes_inplay = tiny_free_reattach_region(&szone->tiny_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_REGION_PAYLOAD_BYTES;
+			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_REGION_PAYLOAD_BYTES;
+			tiny_depot_ptr->mag_num_objects -= objects_in_use;
+
+			recirc_list_splice_last(&szone->tiny_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(&szone->tiny_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);
+		}
+	}
+
+	for (mag_index = 0; mag_index < szone->small_rack.num_magazines; mag_index++) {
+		size_t index;
+		for (index = 0; index < szone->small_rack.region_generation->num_regions_allocated; ++index) {
+			SZONE_LOCK(szone);
+
+			region_t small = szone->small_rack.region_generation->hashed_regions[index];
+			if (!small || small == HASHRING_REGION_DEALLOCATED) {
+				SZONE_UNLOCK(szone);
+				continue;
+			}
+
+			magazine_t *mag_ptr = mag_lock_zine_for_region_trailer(szone->small_rack.magazines,
+					REGION_TRAILER_FOR_SMALL_REGION(small),
+					MAGAZINE_INDEX_FOR_SMALL_REGION(small));
+			SZONE_UNLOCK(szone);
+
+			/* 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_SMALL_REGION(small);
+
+			/* 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 (small == mag_ptr->mag_last_region && (mag_ptr->mag_bytes_free_at_end || mag_ptr->mag_bytes_free_at_start)) {
+				small_finalize_region(&szone->small_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(&szone->small_rack, mag_ptr, REGION_TRAILER_FOR_SMALL_REGION(small));
+			int objects_in_use = small_free_detach_region(&szone->small_rack, mag_ptr, small);
+
+			SZONE_MAGAZINE_PTR_LOCK(small_depot_ptr);
+			MAGAZINE_INDEX_FOR_SMALL_REGION(small) = DEPOT_MAGAZINE_INDEX;
+			REGION_TRAILER_FOR_SMALL_REGION(small)->pinned_to_depot = 0;
+
+			size_t bytes_inplay = small_free_reattach_region(&szone->small_rack, small_depot_ptr, small);
+
+			/* 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 -= SMALL_REGION_PAYLOAD_BYTES;
+			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);
+
+			small_depot_ptr->mag_num_bytes_in_objects += bytes_inplay;
+			small_depot_ptr->num_bytes_in_magazine += SMALL_REGION_PAYLOAD_BYTES;
+			small_depot_ptr->mag_num_objects -= objects_in_use;
+
+			recirc_list_splice_last(&szone->small_rack, small_depot_ptr, REGION_TRAILER_FOR_SMALL_REGION(small));
+
+			/* Actually do the scan, done holding the depot lock, the call will drop the lock
+			 * around the actual madvise syscalls.
+			 */
+			small_free_scan_madvise_free(&szone->small_rack, small_depot_ptr, small);
+
+			/* 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(small_depot_ptr);
+		}
+	}
+#endif
 
 #if CONFIG_LARGE_CACHE
 	if (szone->flotsam_enabled) {
@@ -1431,7 +1165,7 @@
 
 		// stack allocated copy of the death-row cache
 		int idx = szone->large_entry_cache_oldest, idx_max = szone->large_entry_cache_newest;
-		large_entry_t local_entry_cache[LARGE_ENTRY_CACHE_SIZE_HIGH];
+		large_entry_t local_entry_cache[LARGE_ENTRY_CACHE_SIZE];
 
 		memcpy((void *)local_entry_cache, (void *)szone->large_entry_cache, sizeof(local_entry_cache));
 
@@ -1450,7 +1184,7 @@
 		while (idx != idx_max) {
 			mvm_deallocate_pages((void *)local_entry_cache[idx].address, local_entry_cache[idx].size, 0);
 			total += local_entry_cache[idx].size;
-			if (++idx == szone->large_cache_depth) {
+			if (++idx == LARGE_ENTRY_CACHE_SIZE) {
 				idx = 0;
 			}
 		}
@@ -1521,118 +1255,50 @@
 		stats->size_in_use = 0;   // DEPRECATED szone->num_bytes_in_huge_objects;
 		stats->max_size_in_use = stats->size_allocated = 0;
 		return 1;
-	case 4: {
-		size_t s = 0;
-		unsigned t = 0;
-		size_t u = 0;
-		size_t sa = 0;
-
-#if CONFIG_MEDIUM_ALLOCATOR
-		mag_index_t mag_index;
-		if (szone->is_medium_engaged) {
-			for (mag_index = -1; mag_index < szone->medium_rack.num_magazines; mag_index++) {
-				s += szone->medium_rack.magazines[mag_index].mag_bytes_free_at_start;
-				s += szone->medium_rack.magazines[mag_index].mag_bytes_free_at_end;
-				t += szone->medium_rack.magazines[mag_index].mag_num_objects;
-				u += szone->medium_rack.magazines[mag_index].mag_num_bytes_in_objects;
-			}
-		}
-
-		sa = (szone->medium_rack.num_regions - szone->medium_rack.num_regions_dealloc) * MEDIUM_REGION_SIZE;
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
-		stats->blocks_in_use = t;
-		stats->size_in_use = u;
-		stats->size_allocated = sa;
-		stats->max_size_in_use = stats->size_allocated - s;
-		return 1;
-	}}
+	}
 	return 0;
 }
 
-static kern_return_t
-szone_statistics_task(task_t task, vm_address_t zone_address,
-					  memory_reader_t reader, malloc_statistics_t *stats)
-{
-	reader = !reader && task == mach_task_self() ? _malloc_default_reader : reader;
-
-	szone_t *szone;
-	kern_return_t err;
-
-	err = reader(task, zone_address, sizeof(szone_t), (void**)&szone);
-	if (err) return err;
-
+static void
+szone_statistics(szone_t *szone, malloc_statistics_t *stats)
+{
 	size_t large;
+
 	size_t s = 0;
 	unsigned t = 0;
 	size_t u = 0;
 	mag_index_t mag_index;
 
-	magazine_t *mags;
-	err = reader(task, (vm_address_t)szone->tiny_rack.magazines, sizeof(magazine_t) * szone->tiny_rack.num_magazines, (void**)&mags);
-	if (err) return err;
-
 	for (mag_index = -1; mag_index < szone->tiny_rack.num_magazines; mag_index++) {
-		s += mags[mag_index].mag_bytes_free_at_start;
-		s += mags[mag_index].mag_bytes_free_at_end;
-		t += mags[mag_index].mag_num_objects;
-		u += mags[mag_index].mag_num_bytes_in_objects;
-	}
-
-	err = reader(task, (vm_address_t)szone->small_rack.magazines, sizeof(magazine_t) * szone->small_rack.num_magazines, (void**)&mags);
-	if (err) return err;
+		s += szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_start;
+		s += szone->tiny_rack.magazines[mag_index].mag_bytes_free_at_end;
+		t += szone->tiny_rack.magazines[mag_index].mag_num_objects;
+		u += szone->tiny_rack.magazines[mag_index].mag_num_bytes_in_objects;
+	}
 
 	for (mag_index = -1; mag_index < szone->small_rack.num_magazines; mag_index++) {
-		s += mags[mag_index].mag_bytes_free_at_start;
-		s += mags[mag_index].mag_bytes_free_at_end;
-		t += mags[mag_index].mag_num_objects;
-		u += mags[mag_index].mag_num_bytes_in_objects;
-	}
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		for (mag_index = -1; mag_index < szone->medium_rack.num_magazines; mag_index++) {
-			s += szone->medium_rack.magazines[mag_index].mag_bytes_free_at_start;
-			s += szone->medium_rack.magazines[mag_index].mag_bytes_free_at_end;
-			t += szone->medium_rack.magazines[mag_index].mag_num_objects;
-			u += szone->medium_rack.magazines[mag_index].mag_num_bytes_in_objects;
-		}
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
-	large = szone->num_bytes_in_large_objects;
-
-	stats->blocks_in_use = t + szone->num_large_objects_in_use;
+		s += szone->small_rack.magazines[mag_index].mag_bytes_free_at_start;
+		s += szone->small_rack.magazines[mag_index].mag_bytes_free_at_end;
+		t += szone->small_rack.magazines[mag_index].mag_num_objects;
+		u += szone->small_rack.magazines[mag_index].mag_num_bytes_in_objects;
+	}
+
+	large = szone->num_bytes_in_large_objects + 0; // DEPRECATED szone->num_bytes_in_huge_objects;
+
+	stats->blocks_in_use = t + szone->num_large_objects_in_use + 0; // DEPRECATED szone->num_huge_entries;
 	stats->size_in_use = u + large;
 	stats->max_size_in_use = stats->size_allocated =
 			(szone->tiny_rack.num_regions - szone->tiny_rack.num_regions_dealloc) * TINY_REGION_SIZE +
 			(szone->small_rack.num_regions - szone->small_rack.num_regions_dealloc) * SMALL_REGION_SIZE + large;
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		stats->max_size_in_use += (szone->medium_rack.num_regions -
-				szone->medium_rack.num_regions_dealloc) * MEDIUM_REGION_SIZE;
-	}
-#endif
 	// Now we account for the untouched areas
 	stats->max_size_in_use -= s;
-
-	return KERN_SUCCESS;
-}
-
-static void
-szone_statistics(szone_t *szone, malloc_statistics_t *stats)
-{
-	szone_statistics_task(mach_task_self(), (vm_address_t)szone, NULL, stats);
 }
 
 const struct malloc_introspection_t szone_introspect = {
-		(void *)szone_ptr_in_use_enumerator, (void *)szone_good_size, (void *)szone_check, (void *)szone_print_self, szone_log,
+		(void *)szone_ptr_in_use_enumerator, (void *)szone_good_size, (void *)szone_check, (void *)szone_print, szone_log,
 		(void *)szone_force_lock, (void *)szone_force_unlock, (void *)szone_statistics, (void *)szone_locked, NULL, NULL, NULL,
 		NULL, /* Zone enumeration version 7 and forward. */
-		(void *)szone_reinit_lock, // reinit_lock version 9 and forward
-		(void *)szone_print_task,  // print task, version 11 and forward
-		(void *)szone_statistics_task // stats for task, version 12 and forward
+		(void *)szone_reinit_lock, // reinit_lock version 9 and foward
 }; // marked as const to spare the DATA section
 
 szone_t *
@@ -1668,14 +1334,30 @@
 		debug_flags |= DISABLE_ASLR;
 	}
 
-#if CONFIG_MEDIUM_ALLOCATOR || CONFIG_LARGE_CACHE
+#if CONFIG_SMALL_CUTOFF_DYNAMIC || CONFIG_LARGE_CACHE
 	uint64_t memsize = platform_hw_memsize();
-#endif // CONFIG_MEDIUM_ALLOCATOR || CONFIG_LARGE_CACHE
-
-#if CONFIG_MEDIUM_ALLOCATOR
-	szone->is_medium_engaged = (magazine_medium_enabled &&
-			(memsize >= magazine_medium_active_threshold));
-#endif // CONFIG_MEDIUM_ALLOCATOR
+#endif
+
+	bool is_largemem = false;
+#if CONFIG_SMALL_CUTOFF_LARGEMEM
+	is_largemem = true;
+#elif CONFIG_SMALL_CUTOFF_DYNAMIC
+	// TODO: rdar://problem/35395572
+	// switch to largemem thresholds on devices with > 2 cores and > 2gb of memory
+	uint32_t nproc = platform_cpu_count();
+	is_largemem = (nproc > 2) && (memsize > (2ull << 30));
+#endif
+	if (is_largemem) {
+		debug_flags |= MALLOC_EXTENDED_SMALL_SLOTS;
+		szone->is_largemem = 1;
+		szone->large_threshold = LARGE_THRESHOLD_LARGEMEM;
+		szone->vm_copy_threshold = VM_COPY_THRESHOLD_LARGEMEM;
+	} else {
+		debug_flags &= ~MALLOC_EXTENDED_SMALL_SLOTS;
+		szone->is_largemem = 0;
+		szone->large_threshold = LARGE_THRESHOLD;
+		szone->vm_copy_threshold = VM_COPY_THRESHOLD;
+	}
 
 	// Query the number of configured processors.
 	// Uniprocessor case gets just one tiny and one small magazine (whose index is zero). This gives
@@ -1686,26 +1368,9 @@
 	rack_init(&szone->tiny_rack, RACK_TYPE_TINY, num_magazines, debug_flags);
 	rack_init(&szone->small_rack, RACK_TYPE_SMALL, num_magazines, debug_flags);
 
-#if CONFIG_MEDIUM_ALLOCATOR
-	if (szone->is_medium_engaged) {
-		unsigned max_medium_mags = mag_max_medium_magazines();
-		uint32_t num_medium_mags = (max_medium_mags > 1) ?
-				MIN(max_medium_mags, TINY_MAX_MAGAZINES) : 1;
-		rack_init(&szone->medium_rack, RACK_TYPE_MEDIUM, num_medium_mags,
-				debug_flags);
-	}
-#endif // CONFIG_MEDIUM_ALLOCATOR
-
 #if CONFIG_LARGE_CACHE
 	// madvise(..., MADV_REUSABLE) death-row arrivals above this threshold [~0.1%]
 	szone->large_entry_cache_reserve_limit = (size_t)(memsize >> 10);
-	if (memsize >= magazine_large_expanded_cache_threshold) {
-		szone->large_cache_depth = LARGE_ENTRY_CACHE_SIZE_HIGH;
-		szone->large_cache_entry_limit = LARGE_ENTRY_SIZE_ENTRY_LIMIT_HIGH;
-	} else {
-		szone->large_cache_depth = LARGE_ENTRY_CACHE_SIZE_LOW;
-		szone->large_cache_entry_limit = LARGE_ENTRY_SIZE_ENTRY_LIMIT_LOW;
-	}
 
 	/* <rdar://problem/6610904> Reset protection when returning a previous large allocation? */
 	int32_t libSystemVersion = NSVersionOfLinkTimeLibrary("System");
@@ -1719,7 +1384,7 @@
 	// Initialize the security token.
 	szone->cookie = (uintptr_t)malloc_entropy[0];
 
-	szone->basic_zone.version = 12;
+	szone->basic_zone.version = 10;
 	szone->basic_zone.size = (void *)szone_size;
 	szone->basic_zone.malloc = (void *)szone_malloc;
 	szone->basic_zone.calloc = (void *)szone_calloc;