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//===-- local_cache.h -------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef SCUDO_LOCAL_CACHE_H_
#define SCUDO_LOCAL_CACHE_H_
#include "internal_defs.h"
#include "report.h"
#include "stats.h"
namespace scudo {
template <class SizeClassAllocator> struct SizeClassAllocatorLocalCache {
typedef typename SizeClassAllocator::SizeClassMap SizeClassMap;
struct TransferBatch {
static const u32 MaxNumCached = SizeClassMap::MaxNumCachedHint;
void setFromArray(void **Array, u32 N) {
DCHECK_LE(N, MaxNumCached);
for (u32 I = 0; I < N; I++)
Batch[I] = Array[I];
Count = N;
}
void clear() { Count = 0; }
void add(void *P) {
DCHECK_LT(Count, MaxNumCached);
Batch[Count++] = P;
}
void copyToArray(void **Array) const {
for (u32 I = 0; I < Count; I++)
Array[I] = Batch[I];
}
u32 getCount() const { return Count; }
void *get(u32 I) const {
DCHECK_LE(I, Count);
return Batch[I];
}
static u32 getMaxCached(uptr Size) {
return Min(MaxNumCached, SizeClassMap::getMaxCachedHint(Size));
}
TransferBatch *Next;
private:
u32 Count;
void *Batch[MaxNumCached];
};
void initLinkerInitialized(GlobalStats *S, SizeClassAllocator *A) {
Stats.initLinkerInitialized();
if (S)
S->link(&Stats);
Allocator = A;
}
void init(GlobalStats *S, SizeClassAllocator *A) {
memset(this, 0, sizeof(*this));
initLinkerInitialized(S, A);
}
void destroy(GlobalStats *S) {
drain();
if (S)
S->unlink(&Stats);
}
void *allocate(uptr ClassId) {
CHECK_LT(ClassId, NumClasses);
PerClass *C = &PerClassArray[ClassId];
if (C->Count == 0) {
if (UNLIKELY(!refill(C, ClassId)))
return nullptr;
DCHECK_GT(C->Count, 0);
}
// We read ClassSize first before accessing Chunks because it's adjacent to
// Count, while Chunks might be further off (depending on Count). That keeps
// the memory accesses in close quarters.
const uptr ClassSize = C->ClassSize;
void *P = C->Chunks[--C->Count];
// The jury is still out as to whether any kind of PREFETCH here increases
// performance. It definitely decreases performance on Android though.
// if (!SCUDO_ANDROID) PREFETCH(P);
Stats.add(StatAllocated, ClassSize);
return P;
}
void deallocate(uptr ClassId, void *P) {
CHECK_LT(ClassId, NumClasses);
PerClass *C = &PerClassArray[ClassId];
// We still have to initialize the cache in the event that the first heap
// operation in a thread is a deallocation.
initCacheMaybe(C);
if (C->Count == C->MaxCount)
drain(C, ClassId);
// See comment in allocate() about memory accesses.
const uptr ClassSize = C->ClassSize;
C->Chunks[C->Count++] = P;
Stats.sub(StatAllocated, ClassSize);
}
void drain() {
for (uptr I = 0; I < NumClasses; I++) {
PerClass *C = &PerClassArray[I];
while (C->Count > 0)
drain(C, I);
}
}
TransferBatch *createBatch(uptr ClassId, void *B) {
if (ClassId != SizeClassMap::BatchClassId)
B = allocate(SizeClassMap::BatchClassId);
return reinterpret_cast<TransferBatch *>(B);
}
LocalStats &getStats() { return Stats; }
private:
static const uptr NumClasses = SizeClassMap::NumClasses;
struct PerClass {
u32 Count;
u32 MaxCount;
uptr ClassSize;
void *Chunks[2 * TransferBatch::MaxNumCached];
};
PerClass PerClassArray[NumClasses];
LocalStats Stats;
SizeClassAllocator *Allocator;
ALWAYS_INLINE void initCacheMaybe(PerClass *C) {
if (LIKELY(C->MaxCount))
return;
initCache();
DCHECK_NE(C->MaxCount, 0U);
}
NOINLINE void initCache() {
for (uptr I = 0; I < NumClasses; I++) {
PerClass *P = &PerClassArray[I];
const uptr Size = SizeClassAllocator::getSizeByClassId(I);
P->MaxCount = 2 * TransferBatch::getMaxCached(Size);
P->ClassSize = Size;
}
}
void destroyBatch(uptr ClassId, void *B) {
if (ClassId != SizeClassMap::BatchClassId)
deallocate(SizeClassMap::BatchClassId, B);
}
NOINLINE bool refill(PerClass *C, uptr ClassId) {
initCacheMaybe(C);
TransferBatch *B = Allocator->popBatch(this, ClassId);
if (UNLIKELY(!B))
return false;
DCHECK_GT(B->getCount(), 0);
B->copyToArray(C->Chunks);
C->Count = B->getCount();
destroyBatch(ClassId, B);
return true;
}
NOINLINE void drain(PerClass *C, uptr ClassId) {
const u32 Count = Min(C->MaxCount / 2, C->Count);
const uptr FirstIndexToDrain = C->Count - Count;
TransferBatch *B = createBatch(ClassId, C->Chunks[FirstIndexToDrain]);
if (UNLIKELY(!B))
reportOutOfMemory(
SizeClassAllocator::getSizeByClassId(SizeClassMap::BatchClassId));
B->setFromArray(&C->Chunks[FirstIndexToDrain], Count);
C->Count -= Count;
Allocator->pushBatch(ClassId, B);
}
};
} // namespace scudo
#endif // SCUDO_LOCAL_CACHE_H_
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