Re: [PATCH] selftests/seccomp: Pin benchmark to single CPU

On Tue, Feb 06, 2024 at 10:16:19AM +0000, Mark Brown wrote:

On Tue, Feb 06, 2024 at 01:56:47AM -0800, Kees Cook wrote:

...

• /* Set from highest CPU down. */
• for (cpu = ncores - 1; cpu >= 0; cpu--) {

• CPU_ZERO_S(setsz, setp);
  

• CPU_SET_S(cpu, setsz, setp);
  

Is there some particular reason to go from the highest CPU number down? Not that it super matters but the default would be to iterate from 0 and there's a comment but it just says the what not the why.

I was arbitrarily picking a direction and all the examples I could find started at 0, so this would be more (?) out of the way. :P

Without a cpu cgroup, I can't _exclude_ the pinned CPU from other processes, so I was pretending the last CPU will be less likely to be used.