Messages in this thread | | | Date | Sun, 14 Oct 2012 15:51:35 -0700 | From | "Paul E. McKenney" <> | Subject | Re: RCU NOHZ, tsc, and clock_gettime |
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On Fri, Oct 12, 2012 at 02:27:01PM -0400, Prarit Bhargava wrote: > > > 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.
OK -- have you applied John Stultz's suggestions?
Thanx, Paul
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