linux-kernel - Re: [PATCH 4/6] sched/fair: Skip prefer sibling move between SMT group and non-SMT group

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKfTPtBU1Jehye1bY5Ve0hC9_oGKL=SoVRar3Kbs5rhGcEEnAw@mail.gmail.com>
Date:   Tue, 9 May 2023 15:36:35 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Ionela Voinescu <ionela.voinescu@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        naveen.n.rao@...ux.vnet.ibm.com,
        Yicong Yang <yangyicong@...ilicon.com>,
        Barry Song <v-songbaohua@...o.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH 4/6] sched/fair: Skip prefer sibling move between SMT
 group and non-SMT group

On Thu, 4 May 2023 at 18:11, Tim Chen <tim.c.chen@...ux.intel.com> wrote:
>
> From: Tim C Chen <tim.c.chen@...ux.intel.com>
>
> Do not try to move tasks between non SMT sched group and SMT sched
> group for "prefer sibling" load balance.
> Let asym_active_balance_busiest() handle that case properly.
> Otherwise we could get task bouncing back and forth between
> the SMT sched group and non SMT sched group.
>
> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> ---
>  kernel/sched/fair.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 8a325db34b02..58ef7d529731 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10411,8 +10411,12 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
>         /*
>          * Try to move all excess tasks to a sibling domain of the busiest
>          * group's child domain.
> +        *
> +        * Do not try to move between non smt sched group and smt sched
> +        * group. Let asym active balance properly handle that case.
>          */
>         if (sds.prefer_sibling && local->group_type == group_has_spare &&
> +           !asymmetric_groups(sds.busiest, sds.local) &&

Can't you delete SD_PREFER_SIBLING flags when building topology like
SD_ASYM_CPUCAPACITY does ?

Generally speaking  SD_ASYM_CPUCAPACITY and SD_ASYM_PACKING are doing
quite similar thing, it would be good to get one common solution
instead 2 parallel paths

>             busiest->sum_nr_running > local->sum_nr_running + 1)
>                 goto force_balance;
>
> --
> 2.32.0
>