Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS_KICK

[Vincent Guittot]

On 22 December 2017 at 08:56, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Thu, Dec 21, 2017 at 05:23:27PM +0100, Vincent Guittot wrote:
>> Hi Peter,
>>
>> I think that part of the proposal is missing.
>>
>> One goal of the patchset was to kick an update of the stats of idle
>> cpu when a task wake up on a cpu but the statistic has not been
>> updated for a while.
>>
>> That's why there where a call to nohz_kick_needed in the proposal to
>> kick ilb but only for updating blocked load and not a full idle load
>> balance
>>
>> I can't find this call any more in your patchset
>
> Yeah, I took it out because it didn't make sense to me. If you're waking
> to a stale CPU, you're too late.

I agree that's it's too late for the current wake up but that's the
trade off with delaying the wake up until all blocked load has been
updated.

>