On Mon, 12 Jun 2017, Michal Hocko wrote:
> > These are not soft lockups, these are need_resched warnings. We monitor
> > how long need_resched has been set and when a thread takes an excessive
> > amount of time to reschedule after it has been set. A loop of 512 pages
> > with ptl contention and doing {clear,copy}_user_highpage() shows that
> > need_resched can sit without scheduling for an excessive amount of time.
>
> How much is excessive here?
We monitor anything that holds the cpu for more than 1/20th of a second,
but this specific occurrence has been observed for ~1/8th. The majority
of mm/ is quite good in this regard.
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