OS and thread scheduling Effect of OS on thread scheduling and kernel execution

Hi all,

Had a quick question regarding “cuda and OS”. Does the OS have any role to play once the kernel is launched? as in thread scheduling/memory management etc? This may sound stupid, but the reason i am asking this is I have a kernel which takes about 700 ms on xp and 1.4 seconds on win 7 and this is only the kernel execution time. I have gtx 285 on both machines. This seems to be the issue only when different threads work on memory areas which are wide apart.