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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 "list.h"
#include "platform.h"
#include "report.h"
#include "stats.h"
#include "string_utils.h"
namespace scudo {
template <class SizeClassAllocator> struct SizeClassAllocatorLocalCache {
typedef typename SizeClassAllocator::SizeClassMap SizeClassMap;
typedef typename SizeClassAllocator::CompactPtrT CompactPtrT;
void init(GlobalStats *S, SizeClassAllocator *A) {
DCHECK(isEmpty());
Stats.init();
if (LIKELY(S))
S->link(&Stats);
Allocator = A;
initCache();
}
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) {
// Refill half of the number of max cached.
DCHECK_GT(C->MaxCount / 2, 0U);
if (UNLIKELY(!refill(C, ClassId, C->MaxCount / 2)))
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);
}
bool deallocate(uptr ClassId, void *P) {
CHECK_LT(ClassId, NumClasses);
PerClass *C = &PerClassArray[ClassId];
// If the cache is full, drain half of blocks back to the main allocator.
const bool NeedToDrainCache = C->Count == C->MaxCount;
if (NeedToDrainCache)
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);
return NeedToDrainCache;
}
bool isEmpty() const {
for (uptr I = 0; I < NumClasses; ++I)
if (PerClassArray[I].Count)
return false;
return true;
}
void drain() {
// Drain BatchClassId last as it may be needed while draining normal blocks.
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());
}
void *getBatchClassBlock() {
void *B = allocate(BatchClassId);
if (UNLIKELY(!B))
reportOutOfMemory(SizeClassAllocator::getSizeByClassId(BatchClassId));
return B;
}
LocalStats &getStats() { return Stats; }
void getStats(ScopedString *Str) {
bool EmptyCache = true;
for (uptr I = 0; I < NumClasses; ++I) {
if (PerClassArray[I].Count == 0)
continue;
EmptyCache = false;
// The size of BatchClass is set to 0 intentionally. See the comment in
// initCache() for more details.
const uptr ClassSize = I == BatchClassId
? SizeClassAllocator::getSizeByClassId(I)
: PerClassArray[I].ClassSize;
// Note that the string utils don't support printing u16 thus we cast it
// to a common use type uptr.
Str->append(" %02zu (%6zu): cached: %4zu max: %4zu\n", I, ClassSize,
static_cast<uptr>(PerClassArray[I].Count),
static_cast<uptr>(PerClassArray[I].MaxCount));
}
if (EmptyCache)
Str->append(" No block is cached.\n");
}
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;
u16 MaxCount;
// Note: ClassSize is zero for the transfer batch.
uptr ClassSize;
CompactPtrT Chunks[2 * SizeClassMap::MaxNumCachedHint];
};
PerClass PerClassArray[NumClasses] = {};
LocalStats Stats;
SizeClassAllocator *Allocator = nullptr;
NOINLINE void initCache() {
for (uptr I = 0; I < NumClasses; I++) {
PerClass *P = &PerClassArray[I];
const uptr Size = SizeClassAllocator::getSizeByClassId(I);
P->MaxCount = static_cast<u16>(2 * 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, u16 MaxRefill) {
const u16 NumBlocksRefilled =
Allocator->popBlocks(this, ClassId, C->Chunks, MaxRefill);
DCHECK_LE(NumBlocksRefilled, MaxRefill);
C->Count = static_cast<u16>(C->Count + NumBlocksRefilled);
return NumBlocksRefilled != 0;
}
NOINLINE void drain(PerClass *C, uptr ClassId) {
const u16 Count = Min(static_cast<u16>(C->MaxCount / 2), C->Count);
Allocator->pushBlocks(this, ClassId, &C->Chunks[0], Count);
// u16 will be promoted to int by arithmetic type conversion.
C->Count = static_cast<u16>(C->Count - Count);
for (u16 I = 0; I < C->Count; I++)
C->Chunks[I] = C->Chunks[I + Count];
}
};
} // namespace scudo
#endif // SCUDO_LOCAL_CACHE_H_
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