linux-kernel - [PATCH v3 2/6] sched/fair: Optimize checking for group_asym

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Message-Id: <20210513154909.6385-3-ricardo.neri-calderon@linux.intel.com>
Date:   Thu, 13 May 2021 08:49:05 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Quentin Perret <qperret@...gle.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Aubrey Li <aubrey.li@...el.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: [PATCH v3 2/6] sched/fair: Optimize checking for group_asym_packing

sched_asmy_prefer(a, b) returns true if the priority of cpu a is bigger
than the priority of b. dst_cpu belongs to the local group. It follows
that its priority is equal or less than the priority of the preferred
CPU of the local group. Thus, sched_asmy_prefer() always returns false
when called on the local group.

By checking local_group, we can avoid additional checks and invoking
sched_asmy_prefer() when it is not needed.

Cc: Aubrey Li <aubrey.li@...el.com>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Joel Fernandes (Google) <joel@...lfernandes.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Quentin Perret <qperret@...gle.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Reviewed-by: Len Brown <len.brown@...el.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
Changes since v2:
  * Reworded commit message for clarity. (Peter Z)

Changes since v1:
  * None
---
 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 161b92aa1c79..96b023432a1c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8507,7 +8507,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 	}
 
 	/* Check if dst CPU is idle and preferred to this group */
-	if (env->sd->flags & SD_ASYM_PACKING &&
+	if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
 	    env->idle != CPU_NOT_IDLE &&
 	    sgs->sum_h_nr_running &&
 	    sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
-- 
2.17.1