Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

Li, Aubrey
2017-07-12T02:35:44Z

On 2017/7/12 0:09, Frederic Weisbecker wrote:
> On Tue, Jul 11, 2017 at 11:41:57AM +0200, Peter Zijlstra wrote:
>>
>>> - totally from arch_cpu_idle_enter entry to arch_cpu_idle_exit return costs
>>> 9122ns - 15318ns.
>>> --In this period, rcu_idle_enter costs 1985ns - 2262ns, rcu_idle_exit costs
>>> 1813ns - 3507ns
>>
>> Is that the POPF being painful? or something else?
>
> Probably that and the atomic_add_return().
> We thought RCU idle cost is high, but it seems not. But it still has few microseconds
can be saved if we can remove them from fast idle path.

Thanks,
-Aubrey