Messages in this thread | | | Date | Fri, 12 Oct 2012 14:27:01 -0400 | From | Prarit Bhargava <> | Subject | Re: RCU NOHZ, tsc, and clock_gettime |
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> The effect of removing the two functions you noted (on 3.6 and earlier) > is to prevent RCU from checking for dyntick-idle CPUs, likely incurring > a cache miss for each CPU with interrupts disabled. If you have a lot > of CPUs (or even if NR_CPUS is large and you have a smaller number of > CPUs), this can result in user-space-visible delays. >
Paul,
I built a kernel with NR_CPUS=48 and booted on a 48 cpu (logical) system. I do not see a difference in the test -- the variance is AFAICT just as large as if I had run with NR_CPUS=4096.
P.
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