--- libmalloc/libmalloc-140.50.6/src/thresholds.h
+++ libmalloc/libmalloc-166.220.1/src/thresholds.h
@@ -36,7 +36,7 @@
 #define NUM_TINY_CEIL_BLOCKS (1 << SHIFT_TINY_CEIL_BLOCKS)
 
 /* 
- * Small region size defintions.
+ * Small region size definitions.
  *
  * We can only represent up to 1<<15 for msize; but we choose to stay
  * even below that to avoid the convention msize=0 => msize = (1<<15)
@@ -47,15 +47,6 @@
 #define NUM_SMALL_BLOCKS 16319
 #define NUM_SMALL_CEIL_BLOCKS (1 << SHIFT_SMALL_CEIL_BLOCKS)
 #define SMALL_BLOCKS_ALIGN (SHIFT_SMALL_CEIL_BLOCKS + SHIFT_SMALL_QUANTUM) // 23
-
-/*
- * The number of slots in the free-list for small blocks.  To avoid going to
- * vm system as often on large memory machines, increase the number of free list
- * spots above some amount of RAM installed in the system.
- */
-#define NUM_SMALL_SLOTS 32
-#define NUM_SMALL_SLOTS_LARGEMEM 256
-#define SMALL_BITMAP_WORDS 8
 
 #if MALLOC_TARGET_64BIT
 #define NUM_TINY_SLOTS 64 // number of slots for free-lists
@@ -74,20 +65,45 @@
 /*
  * The threshold above which we start allocating from the large
  * "region" (ie. direct vm_allocates). The LARGEMEM size is used
- * on systems that have more than 1GB RAM.
+ * on macOS and 64bit iOS with 16k pages, > 2gb and > 2 cores once
+ * CONFIG_SMALL_CUTOFF_DYNAMIC is enabled (TODO: rdar://problem/35395572)
+ * Must be a multiple of SMALL_QUANTUM (512 bytes)
  */
-#define LARGE_THRESHOLD (15 * 1024)
-#define LARGE_THRESHOLD_LARGEMEM (127 * 1024)
+#if MALLOC_TARGET_IOS
+#if MALLOC_TARGET_64BIT
+#define LARGE_THRESHOLD (15 * 1024)						// <1 * 16k pages
+#define LARGE_THRESHOLD_LARGEMEM (64 * 1024)			//  4 * 16k pages
+#else
+#define LARGE_THRESHOLD (15 * 1024)						// <4 * 4k pages
+#define LARGE_THRESHOLD_LARGEMEM (64 * 1024)			// 16 * 4k pages
+#endif
+#else
+#define LARGE_THRESHOLD (15 * 1024)						//  <4 * 4k pages
+#define LARGE_THRESHOLD_LARGEMEM (127 * 1024)			// <32 * 4k pages
+#endif
+
+/*
+ * The number of slots in the free-list for small blocks.  To avoid going to
+ * vm system as often on large memory machines, increase the number of free list
+ * spots above some amount of RAM installed in the system.
+ */
+#define NUM_SMALL_SLOTS (LARGE_THRESHOLD >> SHIFT_SMALL_QUANTUM)
+#define NUM_SMALL_SLOTS_LARGEMEM (LARGE_THRESHOLD_LARGEMEM >> SHIFT_SMALL_QUANTUM)
 
 /*
  * When all memory is touched after a copy, vm_copy() is always a lose
  * But if the memory is only read, vm_copy() wins over memmove() at 3 or 4 pages
  * (on a G3/300MHz)
  *
- * This must be larger than LARGE_THRESHOLD
+ * This must be >= LARGE_THRESHOLD
  */
-#define VM_COPY_THRESHOLD (40 * 1024)
-#define VM_COPY_THRESHOLD_LARGEMEM (128 * 1024)
+#if MALLOC_TARGET_IOS && MALLOC_TARGET_64BIT
+#define VM_COPY_THRESHOLD (48 * 1024)					// 3 * 16k pages
+#define VM_COPY_THRESHOLD_LARGEMEM (96 * 1024)			// 6 * 16k pages
+#else
+#define VM_COPY_THRESHOLD (40 * 1024)					// 10 * 4k pages
+#define VM_COPY_THRESHOLD_LARGEMEM (128 * 1024) 		// 32 * 4k pages
+#endif
 
 /*
  * Large entry cache (death row) sizes. The large cache is bounded with
@@ -114,20 +130,47 @@
 #define SZONE_FLOTSAM_THRESHOLD_HIGH (1024 * 1024)
 
 /*
+ * The magazine freelist array must be large enough to accomdate the allocation
+ * granularity of both the tiny and small allocators. In addition, the last
+ * slot in the list is special and reserved for coalesced regions bigger than
+ * the overall max allocation size of the allocator.
+ */
+#define MAGAZINE_FREELIST_SLOTS (NUM_SMALL_SLOTS_LARGEMEM + 1)
+#define MAGAZINE_FREELIST_BITMAP_WORDS ((MAGAZINE_FREELIST_SLOTS + 31) >> 5)
+
+/*
  * Density threshold used in determining the level of emptiness before
  * moving regions to the recirc depot.
  */
 #define DENSITY_THRESHOLD(a) \
 	((a) - ((a) >> 2)) // "Emptiness" f = 0.25, so "Density" is (1 - f)*a. Generally: ((a) - ((a) >> -log2(f)))
 
+/*
+ * Minimum number of regions to retain in a recirc depot.
+ */
+#define DEFAULT_RECIRC_RETAINED_REGIONS 2
+
 /* Sanity checks. */
 
-#if (LARGE_THRESHOLD > NUM_SMALL_SLOTS * SMALL_QUANTUM)
-#error LARGE_THRESHOLD should always be less than NUM_SMALL_SLOTS * SMALL_QUANTUM
-#endif
+MALLOC_STATIC_ASSERT(NUM_SMALL_SLOTS_LARGEMEM == LARGE_THRESHOLD_LARGEMEM >> SHIFT_SMALL_QUANTUM,
+		"NUM_SMALL_SLOTS_LARGEMEM must match LARGE_THRESHOLD_LARGEMEM >> SHIFT_SMALL_QUANTUM");
 
-#if (LARGE_THRESHOLD_LARGEMEM > NUM_SMALL_SLOTS_LARGEMEM * SMALL_QUANTUM)
-#error LARGE_THRESHOLD_LARGEMEM should always be less than NUM_SMALL_SLOTS * SMALL_QUANTUM
-#endif
+MALLOC_STATIC_ASSERT(NUM_TINY_SLOTS <= NUM_SMALL_SLOTS_LARGEMEM,
+		"NUM_TINY_SLOTS must be less than or equal to NUM_SMALL_SLOTS_LARGEMEM");
+
+MALLOC_STATIC_ASSERT((LARGE_THRESHOLD % SMALL_QUANTUM) == 0,
+		"LARGE_THRESHOLD must be a multiple of SMALL_QUANTUM");
+MALLOC_STATIC_ASSERT((LARGE_THRESHOLD_LARGEMEM % SMALL_QUANTUM) == 0,
+		"LARGE_THRESHOLD_LARGEMEM must be a multiple of SMALL_QUANTUM");
+
+MALLOC_STATIC_ASSERT((LARGE_THRESHOLD / SMALL_QUANTUM) <= NUM_SMALL_SLOTS,
+		"LARGE_THRESHOLD must be less than NUM_SMALL_SLOTS * SMALL_QUANTUM");
+MALLOC_STATIC_ASSERT((LARGE_THRESHOLD_LARGEMEM / SMALL_QUANTUM) <=  NUM_SMALL_SLOTS_LARGEMEM,
+		"LARGE_THRESHOLD_LARGEMEM must be less than NUM_SMALL_SLOTS * SMALL_QUANTUM");
+
+MALLOC_STATIC_ASSERT(VM_COPY_THRESHOLD >= LARGE_THRESHOLD,
+		"VM_COPY_THRESHOLD must be larger than LARGE_THRESHOLD");
+MALLOC_STATIC_ASSERT(VM_COPY_THRESHOLD_LARGEMEM >= LARGE_THRESHOLD_LARGEMEM,
+		"VM_COPY_THRESHOLD_LARGEMEM must be larger than LARGE_THRESHOLD_LARGEMEM");
 
 #endif // __THRESHOLDS_H