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System: Further improve frame timing consistency

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This commit is contained in:
Connor McLaughlin 2023-01-12 17:44:32 +10:00
parent 559f14d27d
commit 3b038fd27d
2 changed files with 60 additions and 39 deletions
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82
src/common/timer.cpp
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@ -9,6 +9,7 @@
#ifdef _WIN32
#include "windows_headers.h"
#else
#include <errno.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
@ -97,19 +98,18 @@ void Timer::SleepUntil(Value value, bool exact)
{
if (exact)
{
for (;;)
// Even with the high-precision timer, it's not precise enough to wake us up *exactly* when we want
// to. Dropping off the last 0.5ms and spinning for it seems enough on my system (Win11 22H2).
const Value wake_at = value - ConvertMillisecondsToValue(0.5);
Value current = GetCurrentValue();
if (wake_at > current)
SleepUntil(wake_at, false);
// And spin off whatever time is left.
do
{
Value current = GetCurrentValue();
if (current >= value)
break;
// spin for the last 1ms
if ((value - current) > ConvertMillisecondsToValue(1))
{
SleepUntil(value, false);
continue;
}
}
current = GetCurrentValue();
} while (current < value);
}
else
{
@ -187,40 +187,52 @@ void Timer::SleepUntil(Value value, bool exact)
{
if (exact)
{
for (;;)
static constexpr Value min_sleep_time = static_cast<Value>(0.5 * 1000000);
const Value wake_at = value - min_sleep_time;
Value current = GetCurrentValue();
if (wake_at > current)
SleepUntil(wake_at, false);
// And spin off whatever time is left.
do
{
Value current = GetCurrentValue();
if (current >= value)
break;
static constexpr Value min_sleep_time = 1 * 1000000;
// spin for the last 1ms
if ((value - current) > min_sleep_time)
{
SleepUntil(value, false);
continue;
}
}
current = GetCurrentValue();
} while (current < value);
}
else
{
// Apple doesn't have TIMER_ABSTIME, so fall back to nanosleep in such a case.
#ifdef __APPLE__
const Value current_time = GetCurrentValue();
if (value <= current_time)
return;
for (;;)
{
const Value current_time = GetCurrentValue();
if (value <= current_time)
return;
const Value diff = value - current_time;
struct timespec ts;
ts.tv_sec = diff / UINT64_C(1000000000);
ts.tv_nsec = diff % UINT64_C(1000000000);
nanosleep(&ts, nullptr);
const Value diff = value - current_time;
struct timespec ts;
ts.tv_sec = diff / UINT64_C(1000000000);
ts.tv_nsec = diff % UINT64_C(1000000000);
// nanosleep() can return EINTR if interrupted by a signal.
if (nanosleep(&ts, nullptr) == EINTR)
continue;
else
break;
}
#else
struct timespec ts;
ts.tv_sec = value / UINT64_C(1000000000);
ts.tv_nsec = value % UINT64_C(1000000000);
clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts, nullptr);
for (;;)
{
// clock_nanosleep() can return EINTR if interrupted by a signal.
if (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &ts, nullptr) == EINTR)
continue;
else
break;
}
#endif
}
}

17
src/core/system.cpp
View file

@ -1542,10 +1542,13 @@ void System::Execute()
s_presents_since_last_update++;
}
System::UpdatePerformanceCounters();
if (s_throttler_enabled)
System::Throttle();
// Update perf counters *after* throttling, we want to measure from start-of-frame
// to start-of-frame, not end-of-frame to end-of-frame (will be noisy due to different
// amounts of computation happening in each frame).
System::UpdatePerformanceCounters();
}
}
@ -2189,7 +2192,7 @@ void System::Throttle()
// If we're running too slow, advance the next frame time based on the time we lost. Effectively skips
// running those frames at the intended time, because otherwise if we pause in the debugger, we'll run
// hundreds of frames when we resume.
const Common::Timer::Value current_time = Common::Timer::GetCurrentValue();
Common::Timer::Value current_time = Common::Timer::GetCurrentValue();
if (current_time > s_next_frame_time)
{
const Common::Timer::Value diff = static_cast<s64>(current_time) - static_cast<s64>(s_next_frame_time);
@ -2197,7 +2200,13 @@ void System::Throttle()
return;
}
Common::Timer::SleepUntil(s_next_frame_time, true);
// Use a spinwait if we undersleep for all platforms except android.. don't want to burn battery.
// Linux also seems to do a much better job of waking up at the requested time.
#if defined(__linux__) || defined(__ANDROID__)
Common::Timer::SleepUntil(s_next_frame_time, g_settings.display_all_frames);
#else
Common::Timer::SleepUntil(s_next_frame_time, false);
#endif
}
void System::RunFrames()