linux-kernel - [PATCH] psi: update psi irqtime when the irq delta is nozero

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Date:   Thu, 10 Aug 2023 13:15:14 +0000
From:   Lu Jialin <lujialin4@...wei.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>
CC:     Lu Jialin <lujialin4@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] psi: update psi irqtime when the irq delta is nozero

If update psi irqtime whether the irq delta is zero or not, the performance
will be degradation when update_rq_clock_task works frequently.
Therefore, just update psi irqtime whether the irq delta is nozero.
performace test of times(libmicro):
1) without psi_account_irqtime in update_rq_clock_task
[root@...64_perf]# ./times  -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
             prc thr   usecs/call      samples   errors cnt/samp
times          1   1      0.45210          188        0      500

2) psi_account_irqtime in update_rq_clock_task
[root@...64_perf]# ./times  -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
             prc thr   usecs/call      samples   errors cnt/samp
times          1   1      0.49408          196        0      500

3) psi_account_irqtime in update_rq_clock_task when irq delta is nozero
[root@...64_perf]# ./times  -E -C 200 -L -S -W -N "times" -I 200
Running: times# ./../bin-arm64/times -E -C 200 -L -S -W -N times -I 200
             prc thr   usecs/call      samples   errors cnt/samp
times          1   1      0.45158          195        0      500

Signed-off-by: Lu Jialin <lujialin4@...wei.com>
---
 kernel/sched/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c52c2eba7c73..69c4f229d6d1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -722,7 +722,8 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
 
 	rq->prev_irq_time += irq_delta;
 	delta -= irq_delta;
-	psi_account_irqtime(rq->curr, irq_delta);
+	if (irq_delta)
+		psi_account_irqtime(rq->curr, irq_delta);
 	delayacct_irq(rq->curr, irq_delta);
 #endif
 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
-- 
2.34.1