Messages in this thread | | | Date | Thu, 1 Jul 2021 11:34:48 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH] sched/fair: Ensure _sum and _avg values stay consistent |
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On Thu, Jul 01, 2021 at 03:17:16PM +0530, Sachin Sant wrote: > > > > On 24-Jun-2021, at 4:48 PM, Odin Ugedal <odin@uged.al> wrote: > > > > The _sum and _avg values are in general sync together with the PELT > > divider. They are however not always completely in perfect sync, > > resulting in situations where _sum gets to zero while _avg stays > > positive. Such situations are undesirable. > > > > This comes from the fact that PELT will increase period_contrib, also > > increasing the PELT divider, without updating _sum and _avg values to > > stay in perfect sync where (_sum == _avg * divider). However, such PELT > > change will never lower _sum, making it impossible to end up in a > > situation where _sum is zero and _avg is not. > > > > Therefore, we need to ensure that when subtracting load outside PELT, > > that when _sum is zero, _avg is also set to zero. This occurs when > > (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger > > or equal to the current _sum, while the subtracted _avg is smaller than > > the current _avg. > > > > Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> > > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > > Signed-off-by: Odin Ugedal <odin@uged.al> > > Hello Odin, Vincent, > > The issue of kernel warning(during boot) seen on Power sever, reported few days back is not completely fixed. > I am able to recreate this issue with latest 5.13 kernel(which has this fix) > > # git log --oneline kernel/sched/fair.c > a6eaf3850cb1 Merge tag 'sched-urgent-2021-06-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip > 54a728dc5e4f Merge tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip > 1c35b07e6d39 sched/fair: Ensure _sum and _avg values stay consistent <<== >
What was HEAD when you checked this? 1c35b07e6d39 was merged in the 5.14-rc1 merge window so would not be in 5.13.
# 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@vger.kernel.org.
-- Mel Gorman SUSE Labs
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