Messages in this thread | | | Date | Thu, 13 Jul 2017 16:53:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods |
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On Thu, Jul 13, 2017 at 10:48:55PM +0800, Li, Aubrey wrote:
> - totally from arch_cpu_idle_enter entry to arch_cpu_idle_exit return costs > 9122ns - 15318ns. > ---- In this period(arch idle), rcu_idle_enter costs 1985ns - 2262ns, rcu_idle_exit > costs 1813ns - 3507ns > > Besides RCU,
So Paul wants more details on where RCU hurts so we can try to fix.
> the period includes c-state selection on X86, a few timestamp updates > and a few computations in menu governor. Also, deep HW-cstate latency can be up > to 100+ microseconds, even if the system is very busy, CPU still has chance to enter > deep cstate, which I guess some outburst workloads are not happy with it. > > That's my major concern without a fast idle path.
Fixing C-state selection by creating an alternative idle path sounds so very wrong.
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