content/renderer/scheduler/resource_dispatch_throttler.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_
   6 #define CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_
   7
   8 #include <deque>
   9
  10 #include "base/threading/thread_checker.h"
  11 #include "base/time/time.h"
  12 #include "base/timer/timer.h"
  13 #include "content/common/content_export.h"
  14 #include "ipc/ipc_sender.h"
  15
  16 namespace scheduler {
  17 class RendererScheduler;
  18 }
  19
  20 namespace content {
  21
  22 // Utility class for throttling a stream of resource requests targetted to a
  23 // specific IPC sender. The throttling itself is very basic:
  24 //  * When there is no high-priority work imminent to the main thread, as
  25 //    indicated by the RendererScheduler, throttling is disabled.
  26 //  * When >= N requests have been sent in a given time window, requests are
  27 //    throttled. A timer periodically flushes a portion of the queued requests
  28 //    until all such requests have been flushed.
  29 // TODO(jdduke): Remove this class after resource requests become sufficiently
  30 // cheap on the IO thread, crbug.com/440037.
  31 class CONTENT_EXPORT ResourceDispatchThrottler : public IPC::Sender {
  32  public:
  33   // |flush_period| and |max_requests_per_flush| must be strictly positive
  34   // in duration/value.
  35   ResourceDispatchThrottler(IPC::Sender* proxied_sender,
  36                             scheduler::RendererScheduler* scheduler,
  37                             base::TimeDelta flush_period,
  38                             uint32 max_requests_per_flush);
  39   ~ResourceDispatchThrottler() override;
  40
  41   // IPC::Sender implementation:
  42   bool Send(IPC::Message* msg) override;
  43
  44  private:
  45   friend class ResourceDispatchThrottlerForTest;
  46
  47   // Virtual for testing.
  48   virtual base::TimeTicks Now() const;
  49   virtual void ScheduleFlush();
  50
  51   void Flush();
  52   void FlushAll();
  53   bool ForwardMessage(IPC::Message* msg);
  54
  55   base::ThreadChecker thread_checker_;
  56
  57   IPC::Sender* const proxied_sender_;
  58   scheduler::RendererScheduler* const scheduler_;
  59   const base::TimeDelta flush_period_;
  60   const uint32 max_requests_per_flush_;
  61
  62   base::Timer flush_timer_;
  63   base::TimeTicks last_sent_request_time_;
  64   uint32 sent_requests_since_last_flush_;
  65   std::deque<IPC::Message*> throttled_messages_;
  66
  67   DISALLOW_COPY_AND_ASSIGN(ResourceDispatchThrottler);
  68 };
  69
  70 }  // namespace content
  71
  72 #endif  // CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_