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Use nanoseconds for vblank timing

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Avoids locking on-vblank
STL's clock's accuracy can be funky also.
This commit is contained in:
Joshua Ashton 2020-09-05 17:53:27 +01:00 committed by Pierre-Loup A. Griffais
parent 325445a061
commit bb9d0cdf8f
1 changed files with 12 additions and 23 deletions
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33
src/vblankmanager.cpp
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@ -17,8 +17,7 @@
static Display *g_nestedDpy; static Display *g_nestedDpy;
std::mutex g_vblankLock; std::atomic<uint64_t> g_lastVblank;
std::chrono::time_point< std::chrono::system_clock > g_lastVblank;
float g_flVblankDrawBufferMS = 5.0; float g_flVblankDrawBufferMS = 5.0;
@ -26,25 +25,17 @@ void vblankThreadRun( void )
{ {
while ( true ) while ( true )
{ {
std::chrono::time_point< std::chrono::system_clock > lastVblank; uint64_t lastVblank = g_lastVblank;
int usecInterval = 1.0 / g_nOutputRefresh * 1000.0 * 1000.0; uint64_t nsecInterval = uint64_t(1.0 / g_nOutputRefresh * 1000.0 * 1000.0 * 1000.0);
{ lastVblank -= (uint64_t)(g_flVblankDrawBufferMS * 1000 * 1000);
std::unique_lock<std::mutex> lock( g_vblankLock );
lastVblank = g_lastVblank;
}
lastVblank -= std::chrono::microseconds( (int)(g_flVblankDrawBufferMS * 1000) );
std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
std::chrono::system_clock::time_point targetPoint = lastVblank + std::chrono::microseconds( usecInterval );
uint64_t now = get_time_in_nanos();
uint64_t targetPoint = lastVblank + nsecInterval;
while ( targetPoint < now ) while ( targetPoint < now )
{ targetPoint += nsecInterval;
targetPoint += std::chrono::microseconds( usecInterval );
}
std::this_thread::sleep_until( targetPoint ); sleep_until_nanos( targetPoint );
// give the time of vblank to steamcompmgr // give the time of vblank to steamcompmgr
uint64_t vblanktime = get_time_in_nanos(); uint64_t vblanktime = get_time_in_nanos();
@ -67,7 +58,7 @@ void vblankThreadRun( void )
gpuvis_trace_printf( "sent vblank\n" ); gpuvis_trace_printf( "sent vblank\n" );
// Get on the other side of it now // Get on the other side of it now
std::this_thread::sleep_for( std::chrono::microseconds( (int)((g_flVblankDrawBufferMS + 1.0) * 1000) ) ); sleep_for_nanos( (uint64_t)((g_flVblankDrawBufferMS + 1.0) * 1000 * 1000) );
} }
} }
@ -76,7 +67,7 @@ void vblank_init( void )
g_nestedDpy = XOpenDisplay( wlserver_get_nested_display() ); g_nestedDpy = XOpenDisplay( wlserver_get_nested_display() );
assert( g_nestedDpy != nullptr ); assert( g_nestedDpy != nullptr );
g_lastVblank = std::chrono::system_clock::now(); g_lastVblank = get_time_in_nanos();
std::thread vblankThread( vblankThreadRun ); std::thread vblankThread( vblankThreadRun );
vblankThread.detach(); vblankThread.detach();
@ -84,7 +75,5 @@ void vblank_init( void )
void vblank_mark_possible_vblank( void ) void vblank_mark_possible_vblank( void )
{ {
std::unique_lock<std::mutex> lock( g_vblankLock ); g_lastVblank = get_time_in_nanos();
g_lastVblank = std::chrono::system_clock::now();
} }