compiler/utils/arena_allocator.cc

/*
 * Copyright (C) 2013 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 <algorithm>
#include <numeric>

#include "arena_allocator.h"
#include "base/logging.h"
#include "base/mutex.h"
#include "thread-inl.h"
#include <memcheck/memcheck.h>

namespace art {

// Memmap is a bit slower than malloc according to my measurements.
static constexpr bool kUseMemMap = false;
static constexpr bool kUseMemSet = true && kUseMemMap;
static constexpr size_t kValgrindRedZoneBytes = 8;
constexpr size_t Arena::kDefaultSize;

template <bool kCount>
const char* const ArenaAllocatorStatsImpl<kCount>::kAllocNames[] = {
  "Misc       ",
  "BasicBlock ",
  "LIR        ",
  "LIR masks  ",
  "MIR        ",
  "DataFlow   ",
  "GrowList   ",
  "GrowBitMap ",
  "Dalvik2SSA ",
  "DebugInfo  ",
  "Successor  ",
  "RegAlloc   ",
  "Data       ",
  "Preds      ",
  "STL        ",
};

template <bool kCount>
ArenaAllocatorStatsImpl<kCount>::ArenaAllocatorStatsImpl()
    : num_allocations_(0u) {
  std::fill_n(alloc_stats_, arraysize(alloc_stats_), 0u);
}

template <bool kCount>
void ArenaAllocatorStatsImpl<kCount>::Copy(const ArenaAllocatorStatsImpl& other) {
  num_allocations_ = other.num_allocations_;
  std::copy(other.alloc_stats_, other.alloc_stats_ + arraysize(alloc_stats_), alloc_stats_);
}

template <bool kCount>
void ArenaAllocatorStatsImpl<kCount>::RecordAlloc(size_t bytes, ArenaAllocKind kind) {
  alloc_stats_[kind] += bytes;
  ++num_allocations_;
}

template <bool kCount>
size_t ArenaAllocatorStatsImpl<kCount>::NumAllocations() const {
  return num_allocations_;
}

template <bool kCount>
size_t ArenaAllocatorStatsImpl<kCount>::BytesAllocated() const {
  const size_t init = 0u;  // Initial value of the correct type.
  return std::accumulate(alloc_stats_, alloc_stats_ + arraysize(alloc_stats_), init);
}

template <bool kCount>
void ArenaAllocatorStatsImpl<kCount>::Dump(std::ostream& os, const Arena* first,
                                           ssize_t lost_bytes_adjustment) const {
  size_t malloc_bytes = 0u;
  size_t lost_bytes = 0u;
  size_t num_arenas = 0u;
  for (const Arena* arena = first; arena != nullptr; arena = arena->next_) {
    malloc_bytes += arena->Size();
    lost_bytes += arena->RemainingSpace();
    ++num_arenas;
  }
  // The lost_bytes_adjustment is used to make up for the fact that the current arena
  // may not have the bytes_allocated_ updated correctly.
  lost_bytes += lost_bytes_adjustment;
  const size_t bytes_allocated = BytesAllocated();
  os << " MEM: used: " << bytes_allocated << ", allocated: " << malloc_bytes
     << ", lost: " << lost_bytes << "\n";
  size_t num_allocations = NumAllocations();
  if (num_allocations != 0) {
    os << "Number of arenas allocated: " << num_arenas << ", Number of allocations: "
       << num_allocations << ", avg size: " << bytes_allocated / num_allocations << "\n";
  }
  os << "===== Allocation by kind\n";
  COMPILE_ASSERT(arraysize(kAllocNames) == kNumArenaAllocKinds, check_arraysize_kAllocNames);
  for (int i = 0; i < kNumArenaAllocKinds; i++) {
      os << kAllocNames[i] << std::setw(10) << alloc_stats_[i] << "\n";
  }
}

// Explicitly instantiate the used implementation.
template class ArenaAllocatorStatsImpl<kArenaAllocatorCountAllocations>;

Arena::Arena(size_t size)
    : bytes_allocated_(0),
      map_(nullptr),
      next_(nullptr) {
  if (kUseMemMap) {
    std::string error_msg;
    map_ = MemMap::MapAnonymous("dalvik-arena", NULL, size, PROT_READ | PROT_WRITE, false,
                                &error_msg);
    CHECK(map_ != nullptr) << error_msg;
    memory_ = map_->Begin();
    size_ = map_->Size();
  } else {
    memory_ = reinterpret_cast<uint8_t*>(calloc(1, size));
    size_ = size;
  }
}

Arena::~Arena() {
  if (kUseMemMap) {
    delete map_;
  } else {
    free(reinterpret_cast<void*>(memory_));
  }
}

void Arena::Reset() {
  if (bytes_allocated_) {
    if (kUseMemSet || !kUseMemMap) {
      memset(Begin(), 0, bytes_allocated_);
    } else {
      map_->MadviseDontNeedAndZero();
    }
    bytes_allocated_ = 0;
  }
}

ArenaPool::ArenaPool()
    : lock_("Arena pool lock"),
      free_arenas_(nullptr) {
}

ArenaPool::~ArenaPool() {
  while (free_arenas_ != nullptr) {
    auto* arena = free_arenas_;
    free_arenas_ = free_arenas_->next_;
    delete arena;
  }
}

Arena* ArenaPool::AllocArena(size_t size) {
  Thread* self = Thread::Current();
  Arena* ret = nullptr;
  {
    MutexLock lock(self, lock_);
    if (free_arenas_ != nullptr && LIKELY(free_arenas_->Size() >= size)) {
      ret = free_arenas_;
      free_arenas_ = free_arenas_->next_;
    }
  }
  if (ret == nullptr) {
    ret = new Arena(size);
  }
  ret->Reset();
  return ret;
}

void ArenaPool::FreeArenaChain(Arena* first) {
  if (UNLIKELY(RUNNING_ON_VALGRIND > 0)) {
    for (Arena* arena = first; arena != nullptr; arena = arena->next_) {
      VALGRIND_MAKE_MEM_UNDEFINED(arena->memory_, arena->bytes_allocated_);
    }
  }
  if (first != nullptr) {
    Arena* last = first;
    while (last->next_ != nullptr) {
      last = last->next_;
    }
    Thread* self = Thread::Current();
    MutexLock lock(self, lock_);
    last->next_ = free_arenas_;
    free_arenas_ = first;
  }
}

size_t ArenaAllocator::BytesAllocated() const {
  return ArenaAllocatorStats::BytesAllocated();
}

ArenaAllocator::ArenaAllocator(ArenaPool* pool)
  : pool_(pool),
    begin_(nullptr),
    end_(nullptr),
    ptr_(nullptr),
    arena_head_(nullptr),
    running_on_valgrind_(RUNNING_ON_VALGRIND > 0) {
}

void ArenaAllocator::UpdateBytesAllocated() {
  if (arena_head_ != nullptr) {
    // Update how many bytes we have allocated into the arena so that the arena pool knows how
    // much memory to zero out.
    arena_head_->bytes_allocated_ = ptr_ - begin_;
  }
}

void* ArenaAllocator::AllocValgrind(size_t bytes, ArenaAllocKind kind) {
  size_t rounded_bytes = RoundUp(bytes + kValgrindRedZoneBytes, 8);
  if (UNLIKELY(ptr_ + rounded_bytes > end_)) {
    // Obtain a new block.
    ObtainNewArenaForAllocation(rounded_bytes);
    if (UNLIKELY(ptr_ == nullptr)) {
      return nullptr;
    }
  }
  ArenaAllocatorStats::RecordAlloc(rounded_bytes, kind);
  uint8_t* ret = ptr_;
  ptr_ += rounded_bytes;
  // Check that the memory is already zeroed out.
  for (uint8_t* ptr = ret; ptr < ptr_; ++ptr) {
    CHECK_EQ(*ptr, 0U);
  }
  VALGRIND_MAKE_MEM_NOACCESS(ret + bytes, rounded_bytes - bytes);
  return ret;
}

ArenaAllocator::~ArenaAllocator() {
  // Reclaim all the arenas by giving them back to the thread pool.
  UpdateBytesAllocated();
  pool_->FreeArenaChain(arena_head_);
}

void ArenaAllocator::ObtainNewArenaForAllocation(size_t allocation_size) {
  UpdateBytesAllocated();
  Arena* new_arena = pool_->AllocArena(std::max(Arena::kDefaultSize, allocation_size));
  new_arena->next_ = arena_head_;
  arena_head_ = new_arena;
  // Update our internal data structures.
  ptr_ = begin_ = new_arena->Begin();
  end_ = new_arena->End();
}

MemStats::MemStats(const char* name, const ArenaAllocatorStats* stats, const Arena* first_arena,
                   ssize_t lost_bytes_adjustment)
    : name_(name),
      stats_(stats),
      first_arena_(first_arena),
      lost_bytes_adjustment_(lost_bytes_adjustment) {
}

void MemStats::Dump(std::ostream& os) const {
  os << name_ << " stats:\n";
  stats_->Dump(os, first_arena_, lost_bytes_adjustment_);
}

// Dump memory usage stats.
MemStats ArenaAllocator::GetMemStats() const {
  ssize_t lost_bytes_adjustment =
      (arena_head_ == nullptr) ? 0 : (end_ - ptr_) - arena_head_->RemainingSpace();
  return MemStats("ArenaAllocator", this, arena_head_, lost_bytes_adjustment);
}

}  // namespace art