// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/raster/staging_buffer_pool.h"

#include <memory>

#include "base/memory/ptr_util.h"
#include "base/strings/stringprintf.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/trace_event/memory_dump_manager.h"
#include "cc/base/container_util.h"
#include "cc/debug/traced_value.h"
#include "cc/resources/scoped_resource.h"
#include "gpu/command_buffer/client/gles2_interface.h"

namespace cc {
namespace {

// Delay between checking for query result to be available.
const int kCheckForQueryResultAvailableTickRateMs = 1;

// Number of attempts to allow before we perform a check that will wait for
// query to complete.
const int kMaxCheckForQueryResultAvailableAttempts = 256;

// Delay before a staging buffer might be released.
const int kStagingBufferExpirationDelayMs = 1000;

bool CheckForQueryResult(gpu::gles2::GLES2Interface* gl, unsigned query_id) {
  unsigned complete = 1;
  gl->GetQueryObjectuivEXT(query_id, GL_QUERY_RESULT_AVAILABLE_EXT, &complete);
  return !!complete;
}

void WaitForQueryResult(gpu::gles2::GLES2Interface* gl, unsigned query_id) {
  TRACE_EVENT0("cc", "WaitForQueryResult");

  int attempts_left = kMaxCheckForQueryResultAvailableAttempts;
  while (attempts_left--) {
    if (CheckForQueryResult(gl, query_id))
      break;

    // We have to flush the context to be guaranteed that a query result will
    // be available in a finite amount of time.
    gl->ShallowFlushCHROMIUM();

    base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(
        kCheckForQueryResultAvailableTickRateMs));
  }

  unsigned result = 0;
  gl->GetQueryObjectuivEXT(query_id, GL_QUERY_RESULT_EXT, &result);
}

}  // namespace

StagingBuffer::StagingBuffer(const gfx::Size& size, ResourceFormat format)
    : size(size),
      format(format),
      texture_id(0),
      image_id(0),
      query_id(0),
      content_id(0) {}

StagingBuffer::~StagingBuffer() {
  DCHECK_EQ(texture_id, 0u);
  DCHECK_EQ(image_id, 0u);
  DCHECK_EQ(query_id, 0u);
}

void StagingBuffer::DestroyGLResources(gpu::gles2::GLES2Interface* gl) {
  if (query_id) {
    gl->DeleteQueriesEXT(1, &query_id);
    query_id = 0;
  }
  if (image_id) {
    gl->DestroyImageCHROMIUM(image_id);
    image_id = 0;
  }
  if (texture_id) {
    gl->DeleteTextures(1, &texture_id);
    texture_id = 0;
  }
}

void StagingBuffer::OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd,
                                 ResourceFormat format,
                                 bool in_free_list) const {
  if (!gpu_memory_buffer)
    return;

  gfx::GpuMemoryBufferId buffer_id = gpu_memory_buffer->GetId();
  std::string buffer_dump_name =
      base::StringPrintf("cc/one_copy/staging_memory/buffer_%d", buffer_id.id);
  base::trace_event::MemoryAllocatorDump* buffer_dump =
      pmd->CreateAllocatorDump(buffer_dump_name);

  uint64_t buffer_size_in_bytes =
      ResourceUtil::UncheckedSizeInBytes<uint64_t>(size, format);
  buffer_dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
                         base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                         buffer_size_in_bytes);
  buffer_dump->AddScalar("free_size",
                         base::trace_event::MemoryAllocatorDump::kUnitsBytes,
                         in_free_list ? buffer_size_in_bytes : 0);

  // Emit an ownership edge towards a global allocator dump node.
  const uint64_t tracing_process_id =
      base::trace_event::MemoryDumpManager::GetInstance()
          ->GetTracingProcessId();
  base::trace_event::MemoryAllocatorDumpGuid shared_buffer_guid =
      gfx::GetGpuMemoryBufferGUIDForTracing(tracing_process_id, buffer_id);
  pmd->CreateSharedGlobalAllocatorDump(shared_buffer_guid);

  // By creating an edge with a higher |importance| (w.r.t. browser-side dumps)
  // the tracing UI will account the effective size of the buffer to the child.
  const int kImportance = 2;
  pmd->AddOwnershipEdge(buffer_dump->guid(), shared_buffer_guid, kImportance);
}

StagingBufferPool::StagingBufferPool(base::SequencedTaskRunner* task_runner,
                                     ContextProvider* worker_context_provider,
                                     ResourceProvider* resource_provider,
                                     bool use_partial_raster,
                                     int max_staging_buffer_usage_in_bytes)
    : task_runner_(task_runner),
      worker_context_provider_(worker_context_provider),
      resource_provider_(resource_provider),
      use_partial_raster_(use_partial_raster),
      max_staging_buffer_usage_in_bytes_(max_staging_buffer_usage_in_bytes),
      staging_buffer_usage_in_bytes_(0),
      free_staging_buffer_usage_in_bytes_(0),
      staging_buffer_expiration_delay_(
          base::TimeDelta::FromMilliseconds(kStagingBufferExpirationDelayMs)),
      reduce_memory_usage_pending_(false),
      weak_ptr_factory_(this) {
  DCHECK(worker_context_provider_);
  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
      this, "cc::StagingBufferPool", base::ThreadTaskRunnerHandle::Get());
  reduce_memory_usage_callback_ = base::Bind(
      &StagingBufferPool::ReduceMemoryUsage, weak_ptr_factory_.GetWeakPtr());
}

StagingBufferPool::~StagingBufferPool() {
  base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
      this);
}

void StagingBufferPool::Shutdown() {
  base::AutoLock lock(lock_);
  if (buffers_.empty())
    return;

  ReleaseBuffersNotUsedSince(base::TimeTicks() + base::TimeDelta::Max());
  DCHECK_EQ(staging_buffer_usage_in_bytes_, 0);
  DCHECK_EQ(free_staging_buffer_usage_in_bytes_, 0);
}

void StagingBufferPool::ReleaseStagingBuffer(
    std::unique_ptr<StagingBuffer> staging_buffer) {
  base::AutoLock lock(lock_);

  staging_buffer->last_usage = base::TimeTicks::Now();
  busy_buffers_.push_back(std::move(staging_buffer));

  ScheduleReduceMemoryUsage();
}

bool StagingBufferPool::OnMemoryDump(
    const base::trace_event::MemoryDumpArgs& args,
    base::trace_event::ProcessMemoryDump* pmd) {
  base::AutoLock lock(lock_);

  for (const auto* buffer : buffers_) {
    auto in_free_buffers =
        std::find_if(free_buffers_.begin(), free_buffers_.end(),
                     [buffer](const std::unique_ptr<StagingBuffer>& b) {
                       return b.get() == buffer;
                     });
    buffer->OnMemoryDump(pmd, buffer->format,
                         in_free_buffers != free_buffers_.end());
  }

  return true;
}

void StagingBufferPool::AddStagingBuffer(const StagingBuffer* staging_buffer,
                                         ResourceFormat format) {
  lock_.AssertAcquired();

  DCHECK(buffers_.find(staging_buffer) == buffers_.end());
  buffers_.insert(staging_buffer);
  int buffer_usage_in_bytes =
      ResourceUtil::UncheckedSizeInBytes<int>(staging_buffer->size, format);
  staging_buffer_usage_in_bytes_ += buffer_usage_in_bytes;
}

void StagingBufferPool::RemoveStagingBuffer(
    const StagingBuffer* staging_buffer) {
  lock_.AssertAcquired();

  DCHECK(buffers_.find(staging_buffer) != buffers_.end());
  buffers_.erase(staging_buffer);
  int buffer_usage_in_bytes = ResourceUtil::UncheckedSizeInBytes<int>(
      staging_buffer->size, staging_buffer->format);
  DCHECK_GE(staging_buffer_usage_in_bytes_, buffer_usage_in_bytes);
  staging_buffer_usage_in_bytes_ -= buffer_usage_in_bytes;
}

void StagingBufferPool::MarkStagingBufferAsFree(
    const StagingBuffer* staging_buffer) {
  lock_.AssertAcquired();

  int buffer_usage_in_bytes = ResourceUtil::UncheckedSizeInBytes<int>(
      staging_buffer->size, staging_buffer->format);
  free_staging_buffer_usage_in_bytes_ += buffer_usage_in_bytes;
}

void StagingBufferPool::MarkStagingBufferAsBusy(
    const StagingBuffer* staging_buffer) {
  lock_.AssertAcquired();

  int buffer_usage_in_bytes = ResourceUtil::UncheckedSizeInBytes<int>(
      staging_buffer->size, staging_buffer->format);
  DCHECK_GE(free_staging_buffer_usage_in_bytes_, buffer_usage_in_bytes);
  free_staging_buffer_usage_in_bytes_ -= buffer_usage_in_bytes;
}

std::unique_ptr<StagingBuffer> StagingBufferPool::AcquireStagingBuffer(
    const Resource* resource,
    uint64_t previous_content_id) {
  base::AutoLock lock(lock_);

  std::unique_ptr<StagingBuffer> staging_buffer;

  ContextProvider::ScopedContextLock scoped_context(worker_context_provider_);

  gpu::gles2::GLES2Interface* gl = scoped_context.ContextGL();
  DCHECK(gl);

  // Check if any busy buffers have become available.
  if (resource_provider_->use_sync_query()) {
    while (!busy_buffers_.empty()) {
      if (!CheckForQueryResult(gl, busy_buffers_.front()->query_id))
        break;

      MarkStagingBufferAsFree(busy_buffers_.front().get());
      free_buffers_.push_back(PopFront(&busy_buffers_));
    }
  }

  // Wait for memory usage of non-free buffers to become less than the limit.
  while (
      (staging_buffer_usage_in_bytes_ - free_staging_buffer_usage_in_bytes_) >=
      max_staging_buffer_usage_in_bytes_) {
    // Stop when there are no more busy buffers to wait for.
    if (busy_buffers_.empty())
      break;

    if (resource_provider_->use_sync_query()) {
      WaitForQueryResult(gl, busy_buffers_.front()->query_id);
      MarkStagingBufferAsFree(busy_buffers_.front().get());
      free_buffers_.push_back(PopFront(&busy_buffers_));
    } else {
      // Fall-back to glFinish if CHROMIUM_sync_query is not available.
      gl->Finish();
      while (!busy_buffers_.empty()) {
        MarkStagingBufferAsFree(busy_buffers_.front().get());
        free_buffers_.push_back(PopFront(&busy_buffers_));
      }
    }
  }

  // Find a staging buffer that allows us to perform partial raster when
  // using persistent GpuMemoryBuffers.
  if (use_partial_raster_ && previous_content_id) {
    StagingBufferDeque::iterator it = std::find_if(
        free_buffers_.begin(), free_buffers_.end(),
        [previous_content_id](const std::unique_ptr<StagingBuffer>& buffer) {
          return buffer->content_id == previous_content_id;
        });
    if (it != free_buffers_.end()) {
      staging_buffer = std::move(*it);
      free_buffers_.erase(it);
      MarkStagingBufferAsBusy(staging_buffer.get());
    }
  }

  // Find staging buffer of correct size and format.
  if (!staging_buffer) {
    StagingBufferDeque::iterator it =
        std::find_if(free_buffers_.begin(), free_buffers_.end(),
                     [resource](const std::unique_ptr<StagingBuffer>& buffer) {
                       return buffer->size == resource->size() &&
                              buffer->format == resource->format();
                     });
    if (it != free_buffers_.end()) {
      staging_buffer = std::move(*it);
      free_buffers_.erase(it);
      MarkStagingBufferAsBusy(staging_buffer.get());
    }
  }

  // Create new staging buffer if necessary.
  if (!staging_buffer) {
    staging_buffer = base::WrapUnique(
        new StagingBuffer(resource->size(), resource->format()));
    AddStagingBuffer(staging_buffer.get(), resource->format());
  }

  // Release enough free buffers to stay within the limit.
  while (staging_buffer_usage_in_bytes_ > max_staging_buffer_usage_in_bytes_) {
    if (free_buffers_.empty())
      break;

    free_buffers_.front()->DestroyGLResources(gl);
    MarkStagingBufferAsBusy(free_buffers_.front().get());
    RemoveStagingBuffer(free_buffers_.front().get());
    free_buffers_.pop_front();
  }

  return staging_buffer;
}

base::TimeTicks StagingBufferPool::GetUsageTimeForLRUBuffer() {
  lock_.AssertAcquired();

  if (!free_buffers_.empty())
    return free_buffers_.front()->last_usage;

  if (!busy_buffers_.empty())
    return busy_buffers_.front()->last_usage;

  return base::TimeTicks();
}

void StagingBufferPool::ScheduleReduceMemoryUsage() {
  lock_.AssertAcquired();

  if (reduce_memory_usage_pending_)
    return;

  reduce_memory_usage_pending_ = true;

  // Schedule a call to ReduceMemoryUsage at the time when the LRU buffer
  // should be released.
  base::TimeTicks reduce_memory_usage_time =
      GetUsageTimeForLRUBuffer() + staging_buffer_expiration_delay_;
  task_runner_->PostDelayedTask(
      FROM_HERE, reduce_memory_usage_callback_,
      reduce_memory_usage_time - base::TimeTicks::Now());
}

void StagingBufferPool::ReduceMemoryUsage() {
  base::AutoLock lock(lock_);

  reduce_memory_usage_pending_ = false;

  if (free_buffers_.empty() && busy_buffers_.empty())
    return;

  base::TimeTicks current_time = base::TimeTicks::Now();
  ReleaseBuffersNotUsedSince(current_time - staging_buffer_expiration_delay_);

  if (free_buffers_.empty() && busy_buffers_.empty())
    return;

  reduce_memory_usage_pending_ = true;

  // Schedule another call to ReduceMemoryUsage at the time when the next
  // buffer should be released.
  base::TimeTicks reduce_memory_usage_time =
      GetUsageTimeForLRUBuffer() + staging_buffer_expiration_delay_;
  task_runner_->PostDelayedTask(FROM_HERE, reduce_memory_usage_callback_,
                                reduce_memory_usage_time - current_time);
}

void StagingBufferPool::ReleaseBuffersNotUsedSince(base::TimeTicks time) {
  lock_.AssertAcquired();

  {
    ContextProvider::ScopedContextLock scoped_context(worker_context_provider_);

    gpu::gles2::GLES2Interface* gl = scoped_context.ContextGL();
    DCHECK(gl);

    // Note: Front buffer is guaranteed to be LRU so we can stop releasing
    // buffers as soon as we find a buffer that has been used since |time|.
    while (!free_buffers_.empty()) {
      if (free_buffers_.front()->last_usage > time)
        return;

      free_buffers_.front()->DestroyGLResources(gl);
      MarkStagingBufferAsBusy(free_buffers_.front().get());
      RemoveStagingBuffer(free_buffers_.front().get());
      free_buffers_.pop_front();
    }

    while (!busy_buffers_.empty()) {
      if (busy_buffers_.front()->last_usage > time)
        return;

      busy_buffers_.front()->DestroyGLResources(gl);
      RemoveStagingBuffer(busy_buffers_.front().get());
      busy_buffers_.pop_front();
    }
  }
}

}  // namespace cc