[sanitizer] use fewer size classes in the allocator to reduce the memory footprint. There is no all-size-fits-all constant here, but this change is positive or neutral on several large apps I've tested

llvm-svn: 176855

1 files changed, 27 insertions, 25 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.h b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.h
index 0a8d8452f80..6321d318760 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.h
@@ -26,15 +26,15 @@ namespace __sanitizer {
 // SizeClassMap maps allocation sizes into size classes and back.
 // Class 0 corresponds to size 0.
 // Classes 1 - 16 correspond to sizes 16 to 256 (size = class_id * 16).
-// Next 8 classes: 256 + i * 32 (i = 1 to 8).
-// Next 8 classes: 512 + i * 64 (i = 1 to 8).
+// Next 4 classes: 256 + i * 64  (i = 1 to 4).
+// Next 4 classes: 512 + i * 128 (i = 1 to 4).
 // ...
-// Next 8 classes: 2^k + i * 2^(k-3) (i = 1 to 8).
+// Next 4 classes: 2^k + i * 2^(k-2) (i = 1 to 4).
 // Last class corresponds to kMaxSize = 1 << kMaxSizeLog.
 //
 // This structure of the size class map gives us:
 //   - Efficient table-free class-to-size and size-to-class functions.
-//   - Difference between two consequent size classes is betweed 12% and 6%
+//   - Difference between two consequent size classes is betweed 14% and 25%
 //
 // This class also gives a hint to a thread-caching allocator about the amount
 // of chunks that need to be cached per-thread:
@@ -61,24 +61,28 @@ namespace __sanitizer {
 // c15 => s: 240 diff: +16 07% l 7 cached: 256 61440; id 15
 //
 // c16 => s: 256 diff: +16 06% l 8 cached: 256 65536; id 16
-// c17 => s: 288 diff: +32 12% l 8 cached: 227 65376; id 17
-// c18 => s: 320 diff: +32 11% l 8 cached: 204 65280; id 18
-// c19 => s: 352 diff: +32 10% l 8 cached: 186 65472; id 19
-// c20 => s: 384 diff: +32 09% l 8 cached: 170 65280; id 20
-// c21 => s: 416 diff: +32 08% l 8 cached: 157 65312; id 21
-// c22 => s: 448 diff: +32 07% l 8 cached: 146 65408; id 22
-// c23 => s: 480 diff: +32 07% l 8 cached: 136 65280; id 23
+// c17 => s: 320 diff: +64 25% l 8 cached: 204 65280; id 17
+// c18 => s: 384 diff: +64 20% l 8 cached: 170 65280; id 18
+// c19 => s: 448 diff: +64 16% l 8 cached: 146 65408; id 19
 //
-// c24 => s: 512 diff: +32 06% l 9 cached: 128 65536; id 24
-// c25 => s: 576 diff: +64 12% l 9 cached: 113 65088; id 25
-// c26 => s: 640 diff: +64 11% l 9 cached: 102 65280; id 26
-// c27 => s: 704 diff: +64 10% l 9 cached: 93 65472; id 27
-// c28 => s: 768 diff: +64 09% l 9 cached: 85 65280; id 28
-// c29 => s: 832 diff: +64 08% l 9 cached: 78 64896; id 29
-// c30 => s: 896 diff: +64 07% l 9 cached: 73 65408; id 30
-// c31 => s: 960 diff: +64 07% l 9 cached: 68 65280; id 31
+// c20 => s: 512 diff: +64 14% l 9 cached: 128 65536; id 20
+// c21 => s: 640 diff: +128 25% l 9 cached: 102 65280; id 21
+// c22 => s: 768 diff: +128 20% l 9 cached: 85 65280; id 22
+// c23 => s: 896 diff: +128 16% l 9 cached: 73 65408; id 23
 //
-// c32 => s: 1024 diff: +64 06% l 10 cached: 64 65536; id 32
+// c24 => s: 1024 diff: +128 14% l 10 cached: 64 65536; id 24
+// c25 => s: 1280 diff: +256 25% l 10 cached: 51 65280; id 25
+// c26 => s: 1536 diff: +256 20% l 10 cached: 42 64512; id 26
+// c27 => s: 1792 diff: +256 16% l 10 cached: 36 64512; id 27
+//
+// ...
+//
+// c48 => s: 65536 diff: +8192 14% l 16 cached: 1 65536; id 48
+// c49 => s: 81920 diff: +16384 25% l 16 cached: 1 81920; id 49
+// c50 => s: 98304 diff: +16384 20% l 16 cached: 1 98304; id 50
+// c51 => s: 114688 diff: +16384 16% l 16 cached: 1 114688; id 51
+//
+// c52 => s: 131072 diff: +16384 14% l 17 cached: 1 131072; id 52
 
 template <uptr kMaxSizeLog, uptr kMaxNumCachedT, uptr kMaxBytesCachedLog>
 class SizeClassMap {
@@ -87,7 +91,7 @@ class SizeClassMap {
   static const uptr kMinSize = 1 << kMinSizeLog;
   static const uptr kMidSize = 1 << kMidSizeLog;
   static const uptr kMidClass = kMidSize / kMinSize;
-  static const uptr S = 3;
+  static const uptr S = 2;
   static const uptr M = (1 << S) - 1;
 
  public:
@@ -185,10 +189,8 @@ class SizeClassMap {
   }
 };
 
-typedef SizeClassMap<17, 256, 16>
-    DefaultSizeClassMap;
-typedef SizeClassMap<17, 64, 14>
-    CompactSizeClassMap;
+typedef SizeClassMap<17, 256, 16> DefaultSizeClassMap;
+typedef SizeClassMap<17, 64,  14> CompactSizeClassMap;
 template<class SizeClassAllocator> struct SizeClassAllocatorLocalCache;
 
 // Memory allocator statistics