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
13namespace {
14
15// Number of samples to average the most recent capture and encode time
16// over.
17const int kStatisticsWindow = 3;
18
19// The hard limit is 30fps or 33ms per recording cycle.
20const 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.
25const double kRecordingCpuConsumption = 0.5;
26
27}  // namespace
28
29namespace remoting {
30
31// We assume that the number of available cores is constant.
32CaptureScheduler::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
41CaptureScheduler::~CaptureScheduler() {
42}
43
44base::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
57void CaptureScheduler::RecordCaptureTime(base::TimeDelta capture_time) {
58  capture_time_.Record(capture_time.InMilliseconds());
59}
60
61void CaptureScheduler::RecordEncodeTime(base::TimeDelta encode_time) {
62  encode_time_.Record(encode_time.InMilliseconds());
63}
64
65void CaptureScheduler::SetNumOfProcessorsForTest(int num_of_processors) {
66  num_of_processors_ = num_of_processors;
67}
68
69}  // namespace remoting
70