GPU timers and NVidia 257.15 Drivers

[gdewan]

Anyone else having problems with GPU timers under NVidia 257.15 drivers? They are working fine under 197.45 (windows XP, 64 bit) but if I go to 257.15, glGetQueryObjectiv no longer lets me know when a result is available.

[Aleksandar]

On my machines with WinXP x32, Vista x32 and Win7 x64 (8600M, 8600GT, GTX470) everything works perfectly with 257.15 drivers. Furthermore, TimerQuery works better than in previous releases. I had a problem with short intervals where fps should be several hundreds or thousands, but timer returned 0.4, for example. Now (with 257.15) it doesn't appear.

Can you post a peace of your code to check if the usage is correct (although you said that it used to work... :( )?

[Aleksandar]

This is how I get elapsed time


GLint available = 0;

glGetQueryObjectiv(m_iTimeQuery, GL_QUERY_RESULT_AVAILABLE, &available);

if(available)
glGetQueryObjectuiv(m_iTimeQuery, GL_QUERY_RESULT, &m_timeElapsed_ns);

glBeginQuery(GL_TIME_ELAPSED, m_iTimeQuery);

//DrawScene()

glEndQuery(GL_TIME_ELAPSED);

[Jan]

Is that working Aleksander? I mean what if the result is not available, yet, don't you start a new query with the same object and thus overwrite any previous query?

So, if your result is always just not yet ready, won't you destroy any possibility to ever get a result, because you always "cancel" your previous query ?

Jan.

[Aleksandar]

You are right! Starting new query can be done conditionally, according to availability of previous reading. But, because this code measures a frame rate of whole DrawScene function, it always succeeds.

Ok, for the purity reason, let's change the code this way:


Lint available = 0;

glGetQueryObjectiv(m_iTimeQuery, GL_QUERY_RESULT_AVAILABLE, &available);

if(available){
glGetQueryObjectuiv(m_iTimeQuery, GL_QUERY_RESULT, &m_timeElapsed_ns);
glBeginQuery(GL_TIME_ELAPSED, m_iTimeQuery);
}

//DrawScene()

if(available)
glEndQuery(GL_TIME_ELAPSED);

[Aleksandar]

This is the full version of measuring execution time code (with declarations and initialization code).



// -------------
// GLRenderer.h
// -------------
GLuint m_iTimeQuery;
unsigned int m_timeElapsed_ns;


// ---------------
// GLRenderer.cpp
// ---------------

// Prepare scene

glGenQueries(1, &m_iTimeQuery);
glBeginQuery(GL_TIME_ELAPSED, m_iTimeQuery);
//...
glEndQuery(GL_TIME_ELAPSED);

// Draw scene

GLint available = 0;
glGetQueryObjectiv(m_iTimeQuery, GL_QUERY_RESULT_AVAILABLE, &available);

if(available){
glGetQueryObjectuiv(m_iTimeQuery, GL_QUERY_RESULT, &m_timeElapsed_ns);
glBeginQuery(GL_TIME_ELAPSED, m_iTimeQuery);
}

//DrawScene()

if(available)
glEndQuery(GL_TIME_ELAPSED);