linux-kernel - Re: [PATCH 1/2] sched/fair: Use weight of SD_NUMA domain in find_busiest

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Date:   Fri, 3 Dec 2021 15:21:16 +0530
From:   "Gautham R. Shenoy" <gautham.shenoy@....com>
To:     Barry Song <21cnbao@...il.com>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Mike Galbraith <efault@....de>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sched/fair: Use weight of SD_NUMA domain in
 find_busiest_group

Hello Barry,

On Fri, Dec 03, 2021 at 09:38:33PM +1300, Barry Song wrote:
> On Fri, Dec 3, 2021 at 8:27 PM Mel Gorman <mgorman@...hsingularity.net> wrote:
> >
> > find_busiest_group uses the child domain's group weight instead of
> > the sched_domain's weight that has SD_NUMA set when calculating the
> > allowed imbalance between NUMA nodes. This is wrong and inconsistent
> > with find_idlest_group.
> >
> > This patch uses the SD_NUMA weight in both.
> >
> > Fixes: c4e8f691d926 ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCS")

> 
> Hi Mel,
> 
> sorry I might be missing something. but I have failed to figure out
> where this commit is.


I think it is supposed to be

Fixes: 7d2b5dd0bcc4 ("sched/numa: Allow a floating imbalance between NUMA nodes")
since it was the commit which introduced the "busiest->group_weight" change. 

> 
> > Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> > ---
> >  kernel/sched/fair.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 6e476f6d9435..0a969affca76 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -9397,7 +9397,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
> >                 /* Consider allowing a small imbalance between NUMA groups */
> >                 if (env->sd->flags & SD_NUMA) {
> >                         env->imbalance = adjust_numa_imbalance(env->imbalance,
> > -                               busiest->sum_nr_running, busiest->group_weight);
> > +                               busiest->sum_nr_running, env->sd->span_weight);



> >                 }
> >
> >                 return;
> > --
> > 2.31.1
> >
> 
> Thanks
> Barry

--
Thanks and Regards
gautham.