windows xp 64 causing gpu idling?

I’ve run into a problem that is killing my program execution speed. Mainly, my GPU seems to go idle for approximately 15 to 16 milliseconds after running 500 iterations in a single program. Essentially, prior to 500 iterations, my kernels each run in under 1 ms. After 500, it will run two or three iterations at sub millisecond timeframes then do a single iteration at about 15 to 16 ms.

The timeframe looks like this if its confusing

1st 500 iterations: 0 in terms of milliseconds.
501st iter: 0
502nd iter: 0
503rd: 15

and so on until my program ends. I have confirmed that even calling a kernel with nothing in it also results in the same amount of idle time, albeit far more spread apart. The only thing I can think of that this can be is another process/thread preempting my program while its running on the CPU. Has anyone else run into this problem?

what is your timing method? cuda or sth. else?

Noticed it too.
when running my code in cuda profiler I have this “white spots” where - for no reason - GPU is idling, although my host code isn’t doing anything special.

Maybe it is screen display drivver? Try gpu as physX device, use other gpu to display. Also check other os, winxp for example.