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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "malloc_arena_pool.h"
#include <algorithm>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <android-base/logging.h>
#include "arena_allocator-inl.h"
#include "mman.h"
namespace art {
class MallocArena final : public Arena {
public:
explicit MallocArena(size_t size = arena_allocator::kArenaDefaultSize);
virtual ~MallocArena();
private:
static constexpr size_t RequiredOverallocation() {
return (alignof(std::max_align_t) < ArenaAllocator::kArenaAlignment)
? ArenaAllocator::kArenaAlignment - alignof(std::max_align_t)
: 0u;
}
uint8_t* unaligned_memory_;
};
MallocArena::MallocArena(size_t size) {
// We need to guarantee kArenaAlignment aligned allocation for the new arena.
// TODO: Use std::aligned_alloc() when it becomes available with C++17.
constexpr size_t overallocation = RequiredOverallocation();
unaligned_memory_ = reinterpret_cast<uint8_t*>(calloc(1, size + overallocation));
CHECK(unaligned_memory_ != nullptr); // Abort on OOM.
DCHECK_ALIGNED(unaligned_memory_, alignof(std::max_align_t));
if (overallocation == 0u) {
memory_ = unaligned_memory_;
} else {
memory_ = AlignUp(unaligned_memory_, ArenaAllocator::kArenaAlignment);
if (kRunningOnMemoryTool) {
size_t head = memory_ - unaligned_memory_;
size_t tail = overallocation - head;
MEMORY_TOOL_MAKE_NOACCESS(unaligned_memory_, head);
MEMORY_TOOL_MAKE_NOACCESS(memory_ + size, tail);
}
}
DCHECK_ALIGNED(memory_, ArenaAllocator::kArenaAlignment);
size_ = size;
}
MallocArena::~MallocArena() {
constexpr size_t overallocation = RequiredOverallocation();
if (overallocation != 0u && kRunningOnMemoryTool) {
size_t head = memory_ - unaligned_memory_;
size_t tail = overallocation - head;
MEMORY_TOOL_MAKE_UNDEFINED(unaligned_memory_, head);
MEMORY_TOOL_MAKE_UNDEFINED(memory_ + size_, tail);
}
free(reinterpret_cast<void*>(unaligned_memory_));
}
void Arena::Reset() {
if (bytes_allocated_ > 0) {
memset(Begin(), 0, bytes_allocated_);
bytes_allocated_ = 0;
}
}
MallocArenaPool::MallocArenaPool() : free_arenas_(nullptr) {
}
MallocArenaPool::~MallocArenaPool() {
ReclaimMemory();
}
void MallocArenaPool::ReclaimMemory() {
while (free_arenas_ != nullptr) {
Arena* arena = free_arenas_;
free_arenas_ = free_arenas_->next_;
delete arena;
}
}
void MallocArenaPool::LockReclaimMemory() {
std::lock_guard<std::mutex> lock(lock_);
ReclaimMemory();
}
Arena* MallocArenaPool::AllocArena(size_t size) {
Arena* ret = nullptr;
{
std::lock_guard<std::mutex> lock(lock_);
// We used to check only the first free arena but we're now checking two.
//
// FIXME: This is a workaround for `oatdump` running out of memory because of an allocation
// pattern where we would allocate a large arena (more than the default size) and then a
// normal one (default size) and then return them to the pool together, with the normal one
// passed as `first` to `FreeArenaChain()`, thus becoming the first in the `free_arenas_`
// list. Since we checked only the first arena, doing this repeatedly would never reuse the
// existing freed larger arenas and they would just accumulate in the free arena list until
// running out of memory. This workaround allows reusing the second arena in the list, thus
// fixing the problem for this specific allocation pattern. Similar allocation patterns
// with three or more arenas can still result in out of memory issues.
if (free_arenas_ != nullptr && LIKELY(free_arenas_->Size() >= size)) {
ret = free_arenas_;
free_arenas_ = free_arenas_->next_;
} else if (free_arenas_ != nullptr &&
free_arenas_->next_ != nullptr &&
free_arenas_->next_->Size() >= size) {
ret = free_arenas_->next_;
free_arenas_->next_ = free_arenas_->next_->next_;
}
}
if (ret == nullptr) {
ret = new MallocArena(size);
}
ret->Reset();
return ret;
}
void MallocArenaPool::TrimMaps() {
// Nop, because there is no way to do madvise here.
}
size_t MallocArenaPool::GetBytesAllocated() const {
size_t total = 0;
std::lock_guard<std::mutex> lock(lock_);
for (Arena* arena = free_arenas_; arena != nullptr; arena = arena->next_) {
total += arena->GetBytesAllocated();
}
return total;
}
void MallocArenaPool::FreeArenaChain(Arena* first) {
if (kRunningOnMemoryTool) {
for (Arena* arena = first; arena != nullptr; arena = arena->next_) {
MEMORY_TOOL_MAKE_UNDEFINED(arena->memory_, arena->bytes_allocated_);
}
}
if (arena_allocator::kArenaAllocatorPreciseTracking) {
// Do not reuse arenas when tracking.
while (first != nullptr) {
Arena* next = first->next_;
delete first;
first = next;
}
return;
}
if (first != nullptr) {
Arena* last = first;
while (last->next_ != nullptr) {
last = last->next_;
}
std::lock_guard<std::mutex> lock(lock_);
last->next_ = free_arenas_;
free_arenas_ = first;
}
}
} // namespace art
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