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Message-ID: <f8b9c9c6ac533c03edf16cc322069b3670992584.camel@linux.intel.com>
Subject: Re: [PATCH 4/6] sched/fair: Skip prefer sibling move between SMT
 group and non-SMT group
From:   Tim Chen <tim.c.chen@linux.intel.com>
To:     Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Ricardo Neri <ricardo.neri@intel.com>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Len Brown <len.brown@intel.com>, Mel Gorman <mgorman@suse.de>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Valentin Schneider <vschneid@redhat.com>,
        Ionela Voinescu <ionela.voinescu@arm.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Shrikanth Hegde <sshegde@linux.vnet.ibm.com>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        naveen.n.rao@linux.vnet.ibm.com,
        Yicong Yang <yangyicong@hisilicon.com>,
        Barry Song <v-songbaohua@oppo.com>,
        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Date:   Tue, 09 May 2023 16:35:44 -0700
In-Reply-To: <CAKfTPtBU1Jehye1bY5Ve0hC9_oGKL=SoVRar3Kbs5rhGcEEnAw@mail.gmail.com>
References: <cover.1683156492.git.tim.c.chen@linux.intel.com>
         <b20517e3986bfdde8a605afa19d144ec411c7a42.1683156492.git.tim.c.chen@linux.intel.com>
         <CAKfTPtBU1Jehye1bY5Ve0hC9_oGKL=SoVRar3Kbs5rhGcEEnAw@mail.gmail.com>
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On Tue, 2023-05-09 at 15:36 +0200, Vincent Guittot wrote:
> On Thu, 4 May 2023 at 18:11, Tim Chen <tim.c.chen@linux.intel.com> wrote:
> >=20
> >=20
> > 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 busi=
est
> >          * 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 =3D=3D group_has_sp=
are &&
> > +           !asymmetric_groups(sds.busiest, sds.local) &&
>=20
> Can't you delete SD_PREFER_SIBLING flags when building topology like
> SD_ASYM_CPUCAPACITY does ?

The sched domain actually can have a mixture of sched groups with Atom modu=
les
and sched groups with SMT cores.  When comparing sched group of Atom core c=
luster
and Atom core cluster, or SMT core with SMT core, I think we do want the pr=
efer sibling logic.
It is only when we are comparing SMT core and Atom core cluster we
want to skip this. Ricardo, please correct me if I am wrong.

>=20
> 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

Okay. I'll see what I can do to merge the handling.

Tim


>=20
> >             busiest->sum_nr_running > local->sum_nr_running + 1)
> >                 goto force_balance;
> >=20
> > --
> > 2.32.0
> >=20