[PATCH] D90814: scudo: Don't memset previously released cached pages in the secondary allocator.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
pcc added reviewers: cryptoad, eugenis.
Herald added a project: Sanitizers.
Herald added a subscriber: Sanitizers.
pcc requested review of this revision.

There is no need to memset released pages because they are already
zero. On db845c, before:

BM_stdlib_malloc_free_default/131072      34562 ns        34547 ns        20258 bytes_per_second=3.53345G/s

after:

BM_stdlib_malloc_free_default/131072      29618 ns        29589 ns        23485 bytes_per_second=4.12548G/s


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D90814

Files:
  compiler-rt/lib/scudo/standalone/secondary.h


Index: compiler-rt/lib/scudo/standalone/secondary.h
===================================================================
--- compiler-rt/lib/scudo/standalone/secondary.h
+++ compiler-rt/lib/scudo/standalone/secondary.h
@@ -52,7 +52,8 @@
 public:
   void initLinkerInitialized(UNUSED s32 ReleaseToOsInterval) {}
   void init(UNUSED s32 ReleaseToOsInterval) {}
-  bool retrieve(UNUSED uptr Size, UNUSED LargeBlock::Header **H) {
+  bool retrieve(UNUSED uptr Size, UNUSED LargeBlock::Header **H,
+                UNUSED bool *Zeroed) {
     return false;
   }
   bool store(UNUSED LargeBlock::Header *H) { return false; }
@@ -127,7 +128,7 @@
     return EntryCached;
   }
 
-  bool retrieve(uptr Size, LargeBlock::Header **H) {
+  bool retrieve(uptr Size, LargeBlock::Header **H, bool *Zeroed) {
     const uptr PageSize = getPageSizeCached();
     const u32 MaxCount = atomic_load(&MaxEntriesCount, memory_order_relaxed);
     ScopedLock L(Mutex);
@@ -142,6 +143,7 @@
       if (Size < BlockSize - PageSize * 4U)
         continue;
       *H = reinterpret_cast<LargeBlock::Header *>(Entries[I].Block);
+      *Zeroed = Entries[I].Time == 0;
       Entries[I].Block = 0;
       (*H)->BlockEnd = Entries[I].BlockEnd;
       (*H)->MapBase = Entries[I].MapBase;
@@ -330,12 +332,13 @@
 
   if (AlignmentHint < PageSize && Cache.canCache(RoundedSize)) {
     LargeBlock::Header *H;
-    if (Cache.retrieve(RoundedSize, &H)) {
+    bool Zeroed;
+    if (Cache.retrieve(RoundedSize, &H, &Zeroed)) {
       if (BlockEnd)
         *BlockEnd = H->BlockEnd;
       void *Ptr = reinterpret_cast<void *>(reinterpret_cast<uptr>(H) +
                                            LargeBlock::getHeaderSize());
-      if (FillContents)
+      if (FillContents && !Zeroed)
         memset(Ptr, FillContents == ZeroFill ? 0 : PatternFillByte,
                H->BlockEnd - reinterpret_cast<uptr>(Ptr));
       const uptr BlockSize = H->BlockEnd - reinterpret_cast<uptr>(H);


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