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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;
typedef typename SizeClassAllocator::CompactPtrT CompactPtrT;
struct TransferBatch {
static const u32 MaxNumCached = SizeClassMap::MaxNumCachedHint;
void setFromArray(CompactPtrT *Array, u32 N) {
DCHECK_LE(N, MaxNumCached);
Count = N;
memcpy(Batch, Array, sizeof(Batch[0]) * Count);
}
void clear() { Count = 0; }
void add(CompactPtrT P) {
DCHECK_LT(Count, MaxNumCached);
Batch[Count++] = P;
}
void copyToArray(CompactPtrT *Array) const {
memcpy(Array, Batch, sizeof(Batch[0]) * Count);
}
u32 getCount() const { return Count; }
CompactPtrT 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;
CompactPtrT Batch[MaxNumCached];
};
void init(GlobalStats *S, SizeClassAllocator *A) {
DCHECK(isEmpty());
Stats.init();
if (LIKELY(S))
S->link(&Stats);
Allocator = A;
}
void destroy(GlobalStats *S) {
drain();
if (LIKELY(S))
S->unlink(&Stats);
}
void *allocate(uptr ClassId) {
DCHECK_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;
CompactPtrT CompactP = C->Chunks[--C->Count];
Stats.add(StatAllocated, ClassSize);
Stats.sub(StatFree, ClassSize);
return Allocator->decompactPtr(ClassId, CompactP);
}
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++] =
Allocator->compactPtr(ClassId, reinterpret_cast<uptr>(P));
Stats.sub(StatAllocated, ClassSize);
Stats.add(StatFree, ClassSize);
}
bool isEmpty() const {
for (uptr I = 0; I < NumClasses; ++I)
if (PerClassArray[I].Count)
return false;
return true;
}
void drain() {
// Drain BatchClassId last as createBatch can refill it.
for (uptr I = 0; I < NumClasses; ++I) {
if (I == BatchClassId)
continue;
while (PerClassArray[I].Count > 0)
drain(&PerClassArray[I], I);
}
while (PerClassArray[BatchClassId].Count > 0)
drain(&PerClassArray[BatchClassId], BatchClassId);
DCHECK(isEmpty());
}
TransferBatch *createBatch(uptr ClassId, void *B) {
if (ClassId != BatchClassId)
B = allocate(BatchClassId);
return reinterpret_cast<TransferBatch *>(B);
}
LocalStats &getStats() { return Stats; }
private:
static const uptr NumClasses = SizeClassMap::NumClasses;
static const uptr BatchClassId = SizeClassMap::BatchClassId;
struct PerClass {
u32 Count;
u32 MaxCount;
// Note: ClassSize is zero for the transfer batch.
uptr ClassSize;
CompactPtrT Chunks[2 * TransferBatch::MaxNumCached];
};
PerClass PerClassArray[NumClasses] = {};
LocalStats Stats;
SizeClassAllocator *Allocator = nullptr;
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);
if (I != BatchClassId) {
P->ClassSize = Size;
} else {
// ClassSize in this struct is only used for malloc/free stats, which
// should only track user allocations, not internal movements.
P->ClassSize = 0;
}
}
}
void destroyBatch(uptr ClassId, void *B) {
if (ClassId != BatchClassId)
deallocate(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);
C->Count = B->getCount();
B->copyToArray(C->Chunks);
B->clear();
destroyBatch(ClassId, B);
return true;
}
NOINLINE void drain(PerClass *C, uptr ClassId) {
const u32 Count = Min(C->MaxCount / 2, C->Count);
TransferBatch *B =
createBatch(ClassId, Allocator->decompactPtr(ClassId, C->Chunks[0]));
if (UNLIKELY(!B))
reportOutOfMemory(SizeClassAllocator::getSizeByClassId(BatchClassId));
B->setFromArray(&C->Chunks[0], Count);
C->Count -= Count;
for (uptr I = 0; I < C->Count; I++)
C->Chunks[I] = C->Chunks[I + Count];
Allocator->pushBatch(ClassId, B);
}
};
} // namespace scudo
#endif // SCUDO_LOCAL_CACHE_H_
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