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

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Date:   Thu,  4 May 2023 09:09:54 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Tim C Chen <tim.c.chen@...ux.intel.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        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: [PATCH 4/6] sched/fair: Skip prefer sibling move between SMT group and non-SMT group

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