| // Copyright 2006-2008 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "base/message_loop/message_pump_default.h" |
| |
| #include "base/auto_reset.h" |
| #include "base/logging.h" |
| #include "base/synchronization/waitable_event.h" |
| #include "base/time/time.h" |
| #include "base/trace_event/trace_event.h" |
| #include "build/build_config.h" |
| |
| #if BUILDFLAG(IS_APPLE) |
| #include <mach/thread_policy.h> |
| |
| #include "base/apple/mach_logging.h" |
| #include "base/apple/scoped_mach_port.h" |
| #include "base/apple/scoped_nsautorelease_pool.h" |
| #include "base/threading/threading_features.h" |
| #endif |
| |
| namespace base { |
| |
| MessagePumpDefault::MessagePumpDefault() |
| : keep_running_(true), |
| event_(WaitableEvent::ResetPolicy::AUTOMATIC, |
| WaitableEvent::InitialState::NOT_SIGNALED) { |
| event_.declare_only_used_while_idle(); |
| } |
| |
| MessagePumpDefault::~MessagePumpDefault() = default; |
| |
| void MessagePumpDefault::Run(Delegate* delegate) { |
| AutoReset<bool> auto_reset_keep_running(&keep_running_, true); |
| |
| for (;;) { |
| #if BUILDFLAG(IS_APPLE) |
| apple::ScopedNSAutoreleasePool autorelease_pool; |
| #endif |
| |
| Delegate::NextWorkInfo next_work_info = delegate->DoWork(); |
| bool has_more_immediate_work = next_work_info.is_immediate(); |
| if (!keep_running_) { |
| break; |
| } |
| |
| if (has_more_immediate_work) { |
| continue; |
| } |
| |
| delegate->DoIdleWork(); |
| if (!keep_running_) { |
| break; |
| } |
| |
| base::TimeTicks before; |
| bool may_busy_loop = max_busy_loop_time_.is_positive(); |
| if (may_busy_loop) { |
| before = base::TimeTicks::Now(); |
| } |
| |
| if (next_work_info.delayed_run_time.is_max()) { |
| if (ShouldBusyLoop()) { |
| bool signaled = BusyWaitOnEvent(before); |
| if (!signaled) { |
| event_.Wait(); |
| } |
| } else { |
| event_.Wait(); |
| } |
| } else { |
| // Not handling shorter sleeps to keep the code as simple as possible. |
| if (ShouldBusyLoop() && |
| next_work_info.remaining_delay() > max_busy_loop_time_) { |
| bool signaled = BusyWaitOnEvent(before); |
| if (!signaled) { |
| next_work_info.recent_now = base::TimeTicks::Now(); |
| event_.TimedWait(next_work_info.remaining_delay()); |
| } |
| } else { |
| event_.TimedWait(next_work_info.remaining_delay()); |
| } |
| } |
| if (may_busy_loop) { |
| RecordWaitTime(base::TimeTicks::Now() - before); |
| } |
| // Since event_ is auto-reset, we don't need to do anything special here |
| // other than service each delegate method. |
| } |
| } |
| |
| void MessagePumpDefault::Quit() { |
| keep_running_ = false; |
| } |
| |
| void MessagePumpDefault::ScheduleWork() { |
| // Since this can be called on any thread, we need to ensure that our Run |
| // loop wakes up. |
| event_.Signal(); |
| } |
| |
| void MessagePumpDefault::ScheduleDelayedWork( |
| const Delegate::NextWorkInfo& next_work_info) { |
| // Since this is always called from the same thread as Run(), there is nothing |
| // to do as the loop is already running. It will wait in Run() with the |
| // correct timeout when it's out of immediate tasks. |
| // TODO(gab): Consider removing ScheduleDelayedWork() when all pumps function |
| // this way (bit.ly/merge-message-pump-do-work). |
| } |
| |
| void MessagePumpDefault::RecordWaitTime(base::TimeDelta wait_time) { |
| last_wait_time_ = wait_time; |
| constexpr float kAlpha = .9; |
| wait_time_exponential_moving_average_ = |
| kAlpha * wait_time_exponential_moving_average_ + |
| (1. - kAlpha) * wait_time; |
| } |
| |
| bool MessagePumpDefault::ShouldBusyLoop() const { |
| // Should only busy loop when the expected wait time is short. Of course, we |
| // don't know whether it will be, but we have two crude heuristics here: |
| // - Last wait was short, maybe the next one will. Not that if this one is |
| // wrong, it only impacts a single wait. |
| // - Recent waits were short (burst of small tasks with waiting in-between) |
| // |
| // The second one is laggy, both to start and to stop, which is why the first |
| // one is there too, to start busy looping faster. |
| // |
| // One important part though is that to avoid wasting too much power, we |
| // should not busy wait for regular sleeps, for instance animations updating |
| // at 60Hz. |
| return max_busy_loop_time_.is_positive() && |
| (last_wait_time_ < max_busy_loop_time_ || |
| wait_time_exponential_moving_average_ < max_busy_loop_time_); |
| } |
| |
| bool MessagePumpDefault::BusyWaitOnEvent(base::TimeTicks before) { |
| bool signaled = false; |
| { |
| TRACE_EVENT(TRACE_DISABLED_BY_DEFAULT("base"), "BusyWait", |
| "last_wait_time_ms", last_wait_time_.InMillisecondsF(), |
| "wait_time_exponential_moving_average_ms", |
| wait_time_exponential_moving_average_.InMillisecondsF()); |
| do { |
| signaled = event_.TimedWait(base::TimeDelta()); |
| } while (!signaled && |
| (base::TimeTicks::Now() - before) < max_busy_loop_time_); |
| } |
| return signaled; |
| } |
| |
| } // namespace base |