Hi Phy !
On Sun, Feb 18, 2007 at 06:02:17PM -0800, Phy Prabab wrote:
> Hello everyone,
>
> I am trying to set affinity on a program to make sure I can get the
> best use of the cache as possible and to eliminate as much noise as
> possible with running my program. I have tried unsuccessfully to set
> affinity using sched_set/getaffinity and the CPU_SET macros. In
> particular, I can not seem to get the process to use affinity I
> specify as in:
>
> int main () {
> cpu_set_t mask;
> cpu_set_t setmask;
> long long x;
> double foo;
> printf("Mask set to %08lx\n", sched_getaffinity(0, &mask));
> CPU_SET(1, &mask);
> if (sched_setaffinity(0, &mask) == -1) {
> printf("error setting affinity.");
> }
>
> printf("Mask is reset to %08lx\n", sched_getaffinity(0, &mask));
> // do some long lasting calculations ....
>
> return;
> }
>
> No mater what I do, the process is never bond to the processor in
> question as exposed by this little appy and by cat /proc/<pid>/cpu.
> Is this just impossible to do?
>
> Ah, the kernel I am using is RH 2.4.21-37.ELsmp.
I don't know for RH kernel, but the affinity syscalls are not in 2.4
mainline. You can apply the patch without much hassle if you want. It's
in Robert Love's directory :
http://www.kernel.org/pub/linux/kernel/people/rml/cpu-affinity/v2.4/
I believe you'll have to use an -ac patch for RHEL.
> TIA!
> Phy
regards,
Willy
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