Re: [PATCH v3] sched/fair: sanitize vruntime of entity being placed

[Roman Kagan]

On Tue, Feb 21, 2023 at 06:26:11PM +0100, Vincent Guittot wrote:
> On Tue, 21 Feb 2023 at 17:57, Roman Kagan <rkagan@xxxxxxxxx> wrote:
> > What scares me, though, is that I've got a message from the test robot
> > that this commit drammatically affected hackbench results, see the quote
> > below.  I expected the commit not to affect any benchmarks.
> >
> > Any idea what could have caused this change?
> 
> Hmm, It's most probably because se->exec_start is reset after a
> migration and the condition becomes true for newly migrated task
> whereas its vruntime should be after min_vruntime.
> 
> We have missed this condition

Makes sense to me.

But what would then be the reliable way to detect a sched_entity which
has slept for long and risks overflowing in .vruntime comparison?

Thanks,
Roman.



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