runtime/gc/space/bump_pointer_space.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 "bump_pointer_space.h"
#include "bump_pointer_space-inl.h"
#include "mirror/class-inl.h"
#include "mirror/object-inl.h"
#include "thread_list.h"

namespace art {
namespace gc {
namespace space {

BumpPointerSpace* BumpPointerSpace::Create(const std::string& name, size_t capacity) {
  capacity = RoundUp(capacity, kPageSize);
  std::string error_msg;
  MemMap mem_map = MemMap::MapAnonymous(name.c_str(),
                                        capacity,
                                        PROT_READ | PROT_WRITE,
                                        /*low_4gb=*/ true,
                                        &error_msg);
  if (!mem_map.IsValid()) {
    LOG(ERROR) << "Failed to allocate pages for alloc space (" << name << ") of size "
        << PrettySize(capacity) << " with message " << error_msg;
    return nullptr;
  }
  return new BumpPointerSpace(name, std::move(mem_map));
}

BumpPointerSpace* BumpPointerSpace::CreateFromMemMap(const std::string& name, MemMap&& mem_map) {
  return new BumpPointerSpace(name, std::move(mem_map));
}

BumpPointerSpace::BumpPointerSpace(const std::string& name, uint8_t* begin, uint8_t* limit)
    : ContinuousMemMapAllocSpace(name,
                                 MemMap::Invalid(),
                                 begin,
                                 begin,
                                 limit,
                                 kGcRetentionPolicyAlwaysCollect),
      growth_end_(limit),
      objects_allocated_(0), bytes_allocated_(0),
      block_lock_("Block lock"),
      main_block_size_(0),
      num_blocks_(0) {
}

BumpPointerSpace::BumpPointerSpace(const std::string& name, MemMap&& mem_map)
    : ContinuousMemMapAllocSpace(name,
                                 std::move(mem_map),
                                 mem_map.Begin(),
                                 mem_map.Begin(),
                                 mem_map.End(),
                                 kGcRetentionPolicyAlwaysCollect),
      growth_end_(mem_map_.End()),
      objects_allocated_(0), bytes_allocated_(0),
      block_lock_("Block lock", kBumpPointerSpaceBlockLock),
      main_block_size_(0),
      num_blocks_(0) {
}

void BumpPointerSpace::Clear() {
  // Release the pages back to the operating system.
  if (!kMadviseZeroes) {
    memset(Begin(), 0, Limit() - Begin());
  }
  CHECK_NE(madvise(Begin(), Limit() - Begin(), MADV_DONTNEED), -1) << "madvise failed";
  // Reset the end of the space back to the beginning, we move the end forward as we allocate
  // objects.
  SetEnd(Begin());
  objects_allocated_.store(0, std::memory_order_relaxed);
  bytes_allocated_.store(0, std::memory_order_relaxed);
  growth_end_ = Limit();
  {
    MutexLock mu(Thread::Current(), block_lock_);
    num_blocks_ = 0;
    main_block_size_ = 0;
  }
}

void BumpPointerSpace::Dump(std::ostream& os) const {
  os << GetName() << " "
      << reinterpret_cast<void*>(Begin()) << "-" << reinterpret_cast<void*>(End()) << " - "
      << reinterpret_cast<void*>(Limit());
}

mirror::Object* BumpPointerSpace::GetNextObject(mirror::Object* obj) {
  const uintptr_t position = reinterpret_cast<uintptr_t>(obj) + obj->SizeOf();
  return reinterpret_cast<mirror::Object*>(RoundUp(position, kAlignment));
}

size_t BumpPointerSpace::RevokeThreadLocalBuffers(Thread* thread) {
  MutexLock mu(Thread::Current(), block_lock_);
  RevokeThreadLocalBuffersLocked(thread);
  return 0U;
}

size_t BumpPointerSpace::RevokeAllThreadLocalBuffers() {
  Thread* self = Thread::Current();
  MutexLock mu(self, *Locks::runtime_shutdown_lock_);
  MutexLock mu2(self, *Locks::thread_list_lock_);
  // TODO: Not do a copy of the thread list?
  std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
  for (Thread* thread : thread_list) {
    RevokeThreadLocalBuffers(thread);
  }
  return 0U;
}

void BumpPointerSpace::AssertThreadLocalBuffersAreRevoked(Thread* thread) {
  if (kIsDebugBuild) {
    MutexLock mu(Thread::Current(), block_lock_);
    DCHECK(!thread->HasTlab());
  }
}

void BumpPointerSpace::AssertAllThreadLocalBuffersAreRevoked() {
  if (kIsDebugBuild) {
    Thread* self = Thread::Current();
    MutexLock mu(self, *Locks::runtime_shutdown_lock_);
    MutexLock mu2(self, *Locks::thread_list_lock_);
    // TODO: Not do a copy of the thread list?
    std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
    for (Thread* thread : thread_list) {
      AssertThreadLocalBuffersAreRevoked(thread);
    }
  }
}

void BumpPointerSpace::UpdateMainBlock() {
  DCHECK_EQ(num_blocks_, 0U);
  main_block_size_ = Size();
}

// Returns the start of the storage.
uint8_t* BumpPointerSpace::AllocBlock(size_t bytes) {
  bytes = RoundUp(bytes, kAlignment);
  if (!num_blocks_) {
    UpdateMainBlock();
  }
  uint8_t* storage = reinterpret_cast<uint8_t*>(
      AllocNonvirtualWithoutAccounting(bytes + sizeof(BlockHeader)));
  if (LIKELY(storage != nullptr)) {
    BlockHeader* header = reinterpret_cast<BlockHeader*>(storage);
    header->size_ = bytes;  // Write out the block header.
    storage += sizeof(BlockHeader);
    ++num_blocks_;
  }
  return storage;
}

accounting::ContinuousSpaceBitmap::SweepCallback* BumpPointerSpace::GetSweepCallback() {
  UNIMPLEMENTED(FATAL);
  UNREACHABLE();
}

uint64_t BumpPointerSpace::GetBytesAllocated() {
  // Start out pre-determined amount (blocks which are not being allocated into).
  uint64_t total = static_cast<uint64_t>(bytes_allocated_.load(std::memory_order_relaxed));
  Thread* self = Thread::Current();
  MutexLock mu(self, *Locks::runtime_shutdown_lock_);
  MutexLock mu2(self, *Locks::thread_list_lock_);
  std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
  MutexLock mu3(Thread::Current(), block_lock_);
  // If we don't have any blocks, we don't have any thread local buffers. This check is required
  // since there can exist multiple bump pointer spaces which exist at the same time.
  if (num_blocks_ > 0) {
    for (Thread* thread : thread_list) {
      total += thread->GetThreadLocalBytesAllocated();
    }
  }
  return total;
}

uint64_t BumpPointerSpace::GetObjectsAllocated() {
  // Start out pre-determined amount (blocks which are not being allocated into).
  uint64_t total = static_cast<uint64_t>(objects_allocated_.load(std::memory_order_relaxed));
  Thread* self = Thread::Current();
  MutexLock mu(self, *Locks::runtime_shutdown_lock_);
  MutexLock mu2(self, *Locks::thread_list_lock_);
  std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
  MutexLock mu3(Thread::Current(), block_lock_);
  // If we don't have any blocks, we don't have any thread local buffers. This check is required
  // since there can exist multiple bump pointer spaces which exist at the same time.
  if (num_blocks_ > 0) {
    for (Thread* thread : thread_list) {
      total += thread->GetThreadLocalObjectsAllocated();
    }
  }
  return total;
}

void BumpPointerSpace::RevokeThreadLocalBuffersLocked(Thread* thread) {
  objects_allocated_.fetch_add(thread->GetThreadLocalObjectsAllocated(), std::memory_order_relaxed);
  bytes_allocated_.fetch_add(thread->GetThreadLocalBytesAllocated(), std::memory_order_relaxed);
  thread->ResetTlab();
}

bool BumpPointerSpace::AllocNewTlab(Thread* self, size_t bytes) {
  MutexLock mu(Thread::Current(), block_lock_);
  RevokeThreadLocalBuffersLocked(self);
  uint8_t* start = AllocBlock(bytes);
  if (start == nullptr) {
    return false;
  }
  self->SetTlab(start, start + bytes, start + bytes);
  return true;
}

void BumpPointerSpace::LogFragmentationAllocFailure(std::ostream& os,
                                                    size_t /* failed_alloc_bytes */) {
  size_t max_contiguous_allocation = Limit() - End();
  os << "; failed due to fragmentation (largest possible contiguous allocation "
     <<  max_contiguous_allocation << " bytes)";
  // Caller's job to print failed_alloc_bytes.
}

size_t BumpPointerSpace::AllocationSizeNonvirtual(mirror::Object* obj, size_t* usable_size) {
  size_t num_bytes = obj->SizeOf();
  if (usable_size != nullptr) {
    *usable_size = RoundUp(num_bytes, kAlignment);
  }
  return num_bytes;
}

}  // namespace space
}  // namespace gc
}  // namespace art