[compiler-rt] [scudo] Add primary option to enable/disable cache blocks. (PR #129794)

[Jordan R AW via llvm-commits]

================
@@ -184,6 +179,148 @@ template <class SizeClassAllocator> struct SizeClassAllocatorLocalCache {
   }
 };
 
+template <class SizeClassAllocator> struct SizeClassAllocatorNoCache {
+  typedef typename SizeClassAllocator::SizeClassMap SizeClassMap;
+  typedef typename SizeClassAllocator::CompactPtrT CompactPtrT;
+
+  void init(GlobalStats *S, SizeClassAllocator *A) {
+    Stats.init();
+    if (LIKELY(S))
+      S->link(&Stats);
+    Allocator = A;
+    initAllocator();
+  }
+
+  void destroy(GlobalStats *S) {
+    if (LIKELY(S))
+      S->unlink(&Stats);
+  }
+
+  void *allocate(uptr ClassId) {
+    CompactPtrT CompactPtr;
+    uptr NumBlocksPopped = Allocator->popBlocks(this, ClassId, &CompactPtr, 1U);
+    if (NumBlocksPopped == 0)
+      return nullptr;
+    DCHECK_EQ(NumBlocksPopped, 1U);
+    const PerClass *C = &PerClassArray[ClassId];
+    Stats.add(StatAllocated, C->ClassSize);
+    Stats.sub(StatFree, C->ClassSize);
+    return Allocator->decompactPtr(ClassId, CompactPtr);
+  }
+
+  bool deallocate(uptr ClassId, void *P) {
+    CHECK_LT(ClassId, NumClasses);
+
+    if (ClassId == BatchClassId)
+      return deallocateBatchClassBlock(P);
+
+    CompactPtrT CompactPtr =
+        Allocator->compactPtr(ClassId, reinterpret_cast<uptr>(P));
+    Allocator->pushBlocks(this, ClassId, &CompactPtr, 1U);
+    PerClass *C = &PerClassArray[ClassId];
+    Stats.sub(StatAllocated, C->ClassSize);
+    Stats.add(StatFree, C->ClassSize);
+
+    // The following adopts the same strategy of allocator draining as used
+    // in SizeClassAllocatorLocalCache so that use the same hint when doing
+    // a page release.
+    ++C->Count;
+    const bool SuggestDraining = C->Count == C->MaxCount;
+    if (SuggestDraining)
+      C->Count = 0;
+    return SuggestDraining;
+  }
+
+  void *getBatchClassBlock() {
+    PerClass *C = &PerClassArray[BatchClassId];
+    if (C->Count == 0) {
+      const u16 NumBlocksRefilled = Allocator->popBlocks(
+          this, BatchClassId, BatchClassStorage, C->MaxCount);
+      if (NumBlocksRefilled == 0)
+        reportOutOfMemory(SizeClassAllocator::getSizeByClassId(BatchClassId));
+      DCHECK_LE(NumBlocksRefilled, SizeClassMap::MaxNumCachedHint);
+      C->Count = NumBlocksRefilled;
+    }
+
+    const uptr ClassSize = C->ClassSize;
+    CompactPtrT CompactP = BatchClassStorage[--C->Count];
+    Stats.add(StatAllocated, ClassSize);
+    Stats.sub(StatFree, ClassSize);
+
+    return Allocator->decompactPtr(BatchClassId, CompactP);
+  }
+
+  LocalStats &getStats() { return Stats; }
+
+  void getStats(ScopedString *Str) { Str->append("    No block is cached.\n"); }
+
+  bool isEmpty() const {
+    const PerClass *C = &PerClassArray[BatchClassId];
+    return C->Count == 0;
+  }
+  void drain() {
+    PerClass *C = &PerClassArray[BatchClassId];
+    if (C->Count > 0) {
+      Allocator->pushBlocks(this, BatchClassId, BatchClassStorage, C->Count);
+      C->Count = 0;
+    }
+  }
+
+  static u16 getMaxCached(uptr Size) {
+    return Min(SizeClassMap::MaxNumCachedHint,
+               SizeClassMap::getMaxCachedHint(Size));
+  }
+
+private:
+  static const uptr NumClasses = SizeClassMap::NumClasses;
+  static const uptr BatchClassId = SizeClassMap::BatchClassId;
+  struct alignas(SCUDO_CACHE_LINE_SIZE) PerClass {
+    u16 Count = 0;
+    u16 MaxCount;
+    // Note: ClassSize is zero for the transfer batch.
+    uptr ClassSize;
+  };
+  PerClass PerClassArray[NumClasses] = {};
+  // Popping BatchClass blocks requires taking a certain amount of blocks at
+  // once. This restriction comes from how we manage the storing of BatchClass
+  // in the primary allocator. See more details in `popBlocksImpl` in the
+  // primary allocator.
+  CompactPtrT BatchClassStorage[SizeClassMap::MaxNumCachedHint] = {};
+  LocalStats Stats;
+  SizeClassAllocator *Allocator = nullptr;
+
+  bool deallocateBatchClassBlock(void *P) {
+    PerClass *C = &PerClassArray[BatchClassId];
+    // Drain all the blocks.
+    if (C->Count == C->MaxCount) {
+      Allocator->pushBlocks(this, BatchClassId, BatchClassStorage, C->Count);
+      C->Count = 0;
+    }
+    BatchClassStorage[C->Count++] =
----------------
ajordanr-google wrote:

Also Prefer Preincrement: https://llvm.org/docs/CodingStandards.html#prefer-preincrement

https://github.com/llvm/llvm-project/pull/129794