Re: [PATCH] sched/fair: Ensure _sum and _avg values stay consistent

[Vincent Guittot]

On Thu, 1 Jul 2021 at 13:10, Odin Ugedal <odin@xxxxxxx> wrote:
>
> tor. 1. jul. 2021 kl. 12:34 skrev Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>:
> >
> > What was HEAD when you checked this? 1c35b07e6d39 was merged in the
> > 5.14-rc1 merge window so would not be in 5.13.
>
> From the kernel log it looks like he used commit dbe69e433722
> (somewhere in Linus' tree), and that should include my patch. I don't
> think the patches from Vincent in the previous thread have been posted
> properly, and I think those can fix the edge case you are seeing.
>
> This should mitigate some issues:
> https://lore.kernel.org/lkml/20210622143154.GA804@vingu-book/

Yeah this one should help . I will send a proper patch if it fixes your issue

>
> while
> https://lore.kernel.org/lkml/20210623071935.GA29143@vingu-book/
> might also help in some cases as well.
>
> Both of those are needed to make sure that *_avg is zero whenever *_sum is zero.
>
> > # git log v5.13..origin/master --pretty=one | grep 1c35b07e
> > 1c35b07e6d3986474e5635be566e7bc79d97c64d sched/fair: Ensure _sum and _avg values stay consistent
> >
> > It's not tagged for stable and lacks a Fixes: tag so I don't think
> > it'll be automatically picked up for 5.13-stable unless Odin sends it
> > to stable@xxxxxxxxxxxxxxx.
>
> Ahh, so the "Fixes" tag is what makes them pick it up...  Thanks! I am
> fairly new to this, but it does make sense when I think about it. I
> have seen https://www.kernel.org/doc/html/v5.13/process/stable-kernel-rules.html
> before, so I guess I can send it to them to get it into -stable. The
> assertion is not a part of v5.13 either though, so people will not see
> this warning there (but it can still cause fairness issues).
>
> > --
> > Mel Gorman
> > SUSE Labs
>
> Thanks
> Odin