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Subject: Re: [PATCH] sched/fair: Sync load_sum with load_avg after dequeue
From:   Sachin Sant <sachinp@linux.vnet.ibm.com>
In-Reply-To: <20210701171837.32156-1-vincent.guittot@linaro.org>
Date:   Fri, 2 Jul 2021 11:45:28 +0530
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, linux-kernel@vger.kernel.org, odin@uged.al
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Message-Id: <DAABF914-F5D0-4C92-BFE0-341D83B9F3D0@linux.vnet.ibm.com>
References: <20210701171837.32156-1-vincent.guittot@linaro.org>
To:     Vincent Guittot <vincent.guittot@linaro.org>
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> On 01-Jul-2021, at 10:48 PM, Vincent Guittot =
<vincent.guittot@linaro.org> wrote:
>=20
> commit 9e077b52d86a ("sched/pelt: Check that *_avg are null when *_sum =
are")
> reported some inconsitencies between *_avg and *_sum.
>=20
> commit 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay =
consistent")
> fixed some but one remains when dequeuing load.
>=20
> sync the cfs's load_sum with its load_avg after dequeuing the load of =
a
> sched_entity.
>=20
> Fixes: 9e077b52d86a ("sched/pelt: Check that *_avg are null when *_sum =
are")
> Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>=20
> I have been able to trigger a WARN on my system even with the patch
> listed above. This patch fixes it.
> Sachin could you test that it also fixes yours ?
>=20

I ran various LTP stress tests, scheduler tests and kernel compile =
operation for about 5 hours.
Haven=E2=80=99t seen the warning during the testing.

Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>

I have left the tests running, will let it run for few more hours.

Thanks
-Sachin

> kernel/sched/fair.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>=20
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 11d22943753f..48fc7dfc2f66 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3037,8 +3037,9 @@ enqueue_load_avg(struct cfs_rq *cfs_rq, struct =
sched_entity *se)
> static inline void
> dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
> {
> +	u32 divider =3D get_pelt_divider(&se->avg);
> 	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
> -	sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * =
se->avg.load_sum);
> +	cfs_rq->avg.load_sum =3D cfs_rq->avg.load_avg * divider;
> }
> #else
> static inline void
> --=20
> 2.17.1
>=20