Messages in this thread | | | Date | Mon, 23 Jun 2014 10:17:19 -0700 | From | Dave Hansen <> | Subject | Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU |
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On 06/23/2014 09:55 AM, Dave Hansen wrote: > This still has a regression. Commit 1ed70de (from Paul's git tree), > gets a result of 52231880. If I back up two commits to v3.16-rc1 and > revert ac1bea85 (the original culprit) the result goes back up to 57308512. > > So something is still going on here. > > I'll go back and compare the grace period ages to see if I can tell what > is going on.
RCU_TRACE interferes with the benchmark a little bit, and it lowers the delta that the regression causes. So, evaluate this cautiously.
According to rcu_sched/rcugp, the average "age" is:
v3.16-rc1, with ac1bea85 reverted: 10.7 v3.16-rc1, plus e552592e: 6.1
Paul, have you been keeping an eye on rcugp? Even if I run my system with only 10 threads, I still see this basic pattern where the average "age" is lower when I see lower performance. It seems to be a reasonable proxy that could be used instead of waiting on me to re-run tests.
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