remoting/host/capture_scheduler.cc

   1 // Copyright (c) 2011 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 #include "remoting/host/capture_scheduler.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "base/sys_info.h"
  11 #include "base/time/time.h"
  12
  13 namespace {
  14
  15 // Number of samples to average the most recent capture and encode time
  16 // over.
  17 const int kStatisticsWindow = 3;
  18
  19 // The hard limit is 30fps or 33ms per recording cycle.
  20 const int64 kDefaultMinimumIntervalMs = 33;
  21
  22 // Controls how much CPU time we can use for encode and capture.
  23 // Range of this value is between 0 to 1. 0 means using 0% of of all CPUs
  24 // available while 1 means using 100% of all CPUs available.
  25 const double kRecordingCpuConsumption = 0.5;
  26
  27 }  // namespace
  28
  29 namespace remoting {
  30
  31 // We assume that the number of available cores is constant.
  32 CaptureScheduler::CaptureScheduler()
  33     : minimum_interval_(
  34           base::TimeDelta::FromMilliseconds(kDefaultMinimumIntervalMs)),
  35       num_of_processors_(base::SysInfo::NumberOfProcessors()),
  36       capture_time_(kStatisticsWindow),
  37       encode_time_(kStatisticsWindow) {
  38   DCHECK(num_of_processors_);
  39 }
  40
  41 CaptureScheduler::~CaptureScheduler() {
  42 }
  43
  44 base::TimeDelta CaptureScheduler::NextCaptureDelay() {
  45   // Delay by an amount chosen such that if capture and encode times
  46   // continue to follow the averages, then we'll consume the target
  47   // fraction of CPU across all cores.
  48   base::TimeDelta delay = base::TimeDelta::FromMilliseconds(
  49       (capture_time_.Average() + encode_time_.Average()) /
  50       (kRecordingCpuConsumption * num_of_processors_));
  51
  52   if (delay < minimum_interval_)
  53     return minimum_interval_;
  54   return delay;
  55 }
  56
  57 void CaptureScheduler::RecordCaptureTime(base::TimeDelta capture_time) {
  58   capture_time_.Record(capture_time.InMilliseconds());
  59 }
  60
  61 void CaptureScheduler::RecordEncodeTime(base::TimeDelta encode_time) {
  62   encode_time_.Record(encode_time.InMilliseconds());
  63 }
  64
  65 void CaptureScheduler::SetNumOfProcessorsForTest(int num_of_processors) {
  66   num_of_processors_ = num_of_processors;
  67 }
  68
  69 }  // namespace remoting