gpu/command_buffer/service/dawn_caching_interface.h

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef GPU_COMMAND_BUFFER_SERVICE_DAWN_CACHING_INTERFACE_H_
#define GPU_COMMAND_BUFFER_SERVICE_DAWN_CACHING_INTERFACE_H_

#include <dawn/platform/DawnPlatform.h>

#include <memory>
#include <string>

#include "base/containers/flat_map.h"
#include "base/containers/flat_set.h"
#include "base/containers/linked_list.h"
#include "base/functional/callback.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/trace_event/memory_dump_provider.h"
#include "gpu/gpu_gles2_export.h"
#include "gpu/ipc/common/gpu_disk_cache_type.h"

namespace gpu {
namespace webgpu {

class DawnCachingInterfaceFactory;

namespace detail {

// In memory caching backend that is just a thread-safe wrapper around a map
// with a simple LRU eviction algorithm implemented on top. This is the actual
// backing cache for instances of DawnCachingInterface. The eviction queue is
// set up so that the entries in the front are the first entries to be deleted.
class GPU_GLES2_EXPORT DawnCachingBackend
    : public base::RefCounted<DawnCachingBackend> {
 public:
  explicit DawnCachingBackend(size_t max_size);

  size_t LoadData(const std::string& key, void* value_out, size_t value_size);
  void StoreData(const std::string& key, const void* value, size_t value_size);

  void PurgeMemory(
      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);

  void OnMemoryDump(const std::string& dump_name,
                    base::trace_event::ProcessMemoryDump* pmd);

 private:
  // Internal entry class for LRU tracking and holding key/value pair.
  class Entry : public base::LinkNode<Entry> {
   public:
    Entry(const std::string& key, const void* value, size_t value_size);

    const std::string& Key() const;

    size_t TotalSize() const;
    size_t DataSize() const;

    size_t ReadData(void* value_out, size_t value_size) const;

   private:
    const std::string key_;
    const std::string data_;
  };

  // Overrides for transparent flat_set lookups using a string.
  friend bool operator<(const std::unique_ptr<Entry>& lhs,
                        const std::unique_ptr<Entry>& rhs);
  friend bool operator<(const std::unique_ptr<Entry>& lhs,
                        const std::string& rhs);
  friend bool operator<(const std::string& lhs,
                        const std::unique_ptr<Entry>& rhs);

  friend class base::RefCounted<DawnCachingBackend>;
  ~DawnCachingBackend();

  void EvictEntry(Entry* entry) EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  base::Lock mutex_;
  base::flat_set<std::unique_ptr<Entry>> entries_ GUARDED_BY(mutex_);
  base::LinkedList<Entry> lru_ GUARDED_BY(mutex_);

  size_t max_size_ GUARDED_BY(mutex_);
  size_t current_size_ GUARDED_BY(mutex_) = 0;
};

}  // namespace detail

// Provides a wrapper class around an in-memory DawnCachingBackend. This class
// was originally designed to handle both disk and in-memory cache backends, but
// because it lives on the GPU process and does not have permissions (due to
// sandbox restrictions) to disk, the disk functionality was removed. Should it
// become necessary to provide interfaces over a disk level disk_cache::Backend,
// please refer to the file history for reference. Note that the big difference
// between in-memory and disk backends are the sync vs async nature of the two
// respectively. Because we are only handling in-memory backends now, the logic
// can be simplified to handle everything synchronously.
class GPU_GLES2_EXPORT DawnCachingInterface
    : public dawn::platform::CachingInterface {
 public:
  using CacheBlobCallback =
      base::RepeatingCallback<void(const std::string& key,
                                   const std::string& blob)>;

  ~DawnCachingInterface() override;

  size_t LoadData(const void* key,
                  size_t key_size,
                  void* value_out,
                  size_t value_size) override;

  void StoreData(const void* key,
                 size_t key_size,
                 const void* value,
                 size_t value_size) override;

 private:
  friend class DawnCachingInterfaceFactory;

  // Simplified accessor to the backend.
  detail::DawnCachingBackend* backend() { return backend_.get(); }

  // Constructor is private because creation of interfaces should be deferred to
  // the factory.
  explicit DawnCachingInterface(
      scoped_refptr<detail::DawnCachingBackend> backend,
      CacheBlobCallback callback = {});

  // Caching interface owns a reference to the backend.
  scoped_refptr<detail::DawnCachingBackend> backend_ = nullptr;

  // The callback provides ability to store cache entries to persistent disk.
  CacheBlobCallback cache_blob_callback_;
};

// Factory class for producing and managing DawnCachingInterfaces.
// Creating/using caching interfaces through the factory guarantees that we will
// not run into issues where backends are being initialized with the same
// parameters leading to blockage.
class GPU_GLES2_EXPORT DawnCachingInterfaceFactory
    : public base::trace_event::MemoryDumpProvider {
 public:
  // Factory for backend creation, especially for testing.
  using BackendFactory =
      base::RepeatingCallback<scoped_refptr<detail::DawnCachingBackend>()>;

  explicit DawnCachingInterfaceFactory(BackendFactory factory);
  DawnCachingInterfaceFactory();
  ~DawnCachingInterfaceFactory() override;

  // Returns a pointer to a DawnCachingInterface, creating a backend for it if
  // necessary. For handle based instances, the factory keeps a reference to the
  // backend until ReleaseHandle below is called.
  std::unique_ptr<DawnCachingInterface> CreateInstance(
      const gpu::GpuDiskCacheHandle& handle,
      DawnCachingInterface::CacheBlobCallback callback = {});

  // Returns a pointer to a DawnCachingInterface that owns the in memory
  // backend. This is used for incognito cases where the cache should not be
  // persisted to disk.
  std::unique_ptr<DawnCachingInterface> CreateInstance();

  // Releases the factory held reference of the handle's backend. Generally this
  // is the last reference which means that the in-memory disk cache will be
  // destroyed and the resources reclaimed. The factory needs to hold an extra
  // reference in order to avoid potential races where the browser may be about
  // to reuse the same handle, but the last reference on the GPU side has just
  // been released causing us to clear the in-memory disk cache too early. When
  // that happens, the disk cache entries are not re-sent over to the GPU
  // process. To avoid this, when the browser's last reference goes away, it
  // notifies the GPU process, and the last reference held by the factory is
  // released.
  void ReleaseHandle(const gpu::GpuDiskCacheHandle& handle);

  void PurgeMemory(
      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);

  // base::trace_event::MemoryDumpProvider implementation.
  bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                    base::trace_event::ProcessMemoryDump* pmd) override;

 private:
  // Creates a default backend for assignment.
  static scoped_refptr<detail::DawnCachingBackend>
  CreateDefaultInMemoryBackend();

  // Factory to create backends.
  BackendFactory backend_factory_;

  // Map that holds existing backends.
  base::flat_map<gpu::GpuDiskCacheHandle,
                 scoped_refptr<detail::DawnCachingBackend>>
      backends_;
};

}  // namespace webgpu
}  // namespace gpu

#endif  // GPU_COMMAND_BUFFER_SERVICE_DAWN_CACHING_INTERFACE_H_