1 // Copyright 2018 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 "base/task_scheduler/service_thread.h"
6
7 #include "base/bind.h"
8 #include "base/bind_helpers.h"
9 #include "base/debug/alias.h"
10 #include "base/rand_util.h"
11 #include "base/stl_util.h"
12 #include "base/task_scheduler/post_task.h"
13 #include "base/task_scheduler/task_scheduler.h"
14 #include "base/task_scheduler/task_tracker.h"
15 #include "base/task_scheduler/task_traits.h"
16 #include "build/build_config.h"
17
18 namespace base {
19 namespace internal {
20
21 namespace {
22
23 TimeDelta g_heartbeat_for_testing = TimeDelta();
24
25 } // namespace
26
ServiceThread(const TaskTracker * task_tracker)27 ServiceThread::ServiceThread(const TaskTracker* task_tracker)
28 : Thread("TaskSchedulerServiceThread"), task_tracker_(task_tracker) {}
29
30 // static
SetHeartbeatIntervalForTesting(TimeDelta heartbeat)31 void ServiceThread::SetHeartbeatIntervalForTesting(TimeDelta heartbeat) {
32 g_heartbeat_for_testing = heartbeat;
33 }
34
Init()35 void ServiceThread::Init() {
36 // In unit tests we sometimes do not have a fully functional TaskScheduler
37 // environment, do not perform the heartbeat report in that case since it
38 // relies on such an environment.
39 if (task_tracker_ && TaskScheduler::GetInstance()) {
40 // Seemingly causing power regression on Android, disable to see if truly at
41 // fault : https://crbug.com/848255
42 #if !defined(OS_ANDROID)
43 // Compute the histogram every hour (with a slight offset to drift if that
44 // hour tick happens to line up with specific events). Once per hour per
45 // user was deemed sufficient to gather a reliable metric.
46 constexpr TimeDelta kHeartbeat = TimeDelta::FromMinutes(59);
47
48 heartbeat_latency_timer_.Start(
49 FROM_HERE,
50 g_heartbeat_for_testing.is_zero() ? kHeartbeat
51 : g_heartbeat_for_testing,
52 BindRepeating(&ServiceThread::PerformHeartbeatLatencyReport,
53 Unretained(this)));
54 #endif
55 }
56 }
57
Run(RunLoop * run_loop)58 NOINLINE void ServiceThread::Run(RunLoop* run_loop) {
59 const int line_number = __LINE__;
60 Thread::Run(run_loop);
61 base::debug::Alias(&line_number);
62 }
63
PerformHeartbeatLatencyReport() const64 void ServiceThread::PerformHeartbeatLatencyReport() const {
65 static constexpr TaskTraits kReportedTraits[] = {
66 {TaskPriority::BACKGROUND}, {TaskPriority::BACKGROUND, MayBlock()},
67 {TaskPriority::USER_VISIBLE}, {TaskPriority::USER_VISIBLE, MayBlock()},
68 {TaskPriority::USER_BLOCKING}, {TaskPriority::USER_BLOCKING, MayBlock()}};
69
70 // Only record latency for one set of TaskTraits per report to avoid bias in
71 // the order in which tasks are posted (should we record all at once) as well
72 // as to avoid spinning up many worker threads to process this report if the
73 // scheduler is currently idle (each pool keeps at least one idle thread so a
74 // single task isn't an issue).
75
76 // Invoke RandInt() out-of-line to ensure it's obtained before
77 // TimeTicks::Now().
78 const TaskTraits& profiled_traits =
79 kReportedTraits[RandInt(0, base::size(kReportedTraits) - 1)];
80
81 // Post through the static API to time the full stack. Use a new Now() for
82 // every set of traits in case PostTaskWithTraits() itself is slow.
83 // Bonus: this appraoch also includes the overhead of Bind() in the reported
84 // latency).
85 base::PostTaskWithTraits(
86 FROM_HERE, profiled_traits,
87 BindOnce(&TaskTracker::RecordLatencyHistogram, Unretained(task_tracker_),
88 TaskTracker::LatencyHistogramType::HEARTBEAT_LATENCY,
89 profiled_traits, TimeTicks::Now()));
90 }
91
92 } // namespace internal
93 } // namespace base
94