Re: [Question]: try to fix contention between expire_timers and try_to_del_timer_sync

[Vikram Mulukutla]

Hi Will,

On 2017-07-31 06:13, Will Deacon wrote:
> Hi Vikram,
>
> On Fri, Jul 28, 2017 at 12:09:38PM -0700, Vikram Mulukutla wrote:
> > On 2017-07-28 02:28, Will Deacon wrote:
> > >On Thu, Jul 27, 2017 at 06:10:34PM -0700, Vikram Mulukutla wrote:

> > >
> > This does seem to help. Here's some data after 5 runs with and without 
> > the
> > patch.
>
> Blimey, that does seem to make a difference. Shame it's so ugly! Would 
> you
> be able to experiment with other values for CPU_RELAX_WFE_THRESHOLD? I 
> had
> it set to 10000 in the diff I posted, but that might be higher than 
> optimal.
> It would be interested to see if it correlates with num_possible_cpus()
> for the highly contended case.
>
> Will

Sorry for the late response - I should hopefully have some more data 
with
different thresholds before the week is finished or on Monday.

Thanks,
Vikram
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