From: Frederic Weisbecker <frederic@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Scott Wood <swood@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH] timers/nohz: Update nohz load even if tick already stopped
Date: Mon, 28 Oct 2019 16:07:16 +0100 [thread overview]
Message-ID: <20191028150716.22890-1-frederic@kernel.org> (raw)
From: Scott Wood <swood@redhat.com>
The way loadavg is tracked during nohz only pays attention to the load
upon entering nohz. This can be particularly noticeable if nohz is
entered while non-idle, and then the cpu goes idle and stays that way for
a long time. We've had reports of a loadavg near 150 on a mostly idle
system.
Calling calc_load_nohz_start() regardless of whether the tick is already
stopped addresses the issue when going idle. Tracking load changes when
not going idle (e.g. multiple SCHED_FIFO tasks coming and going) is not
addressed by this patch.
Signed-off-by: Scott Wood <swood@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/time/tick-sched.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index c2748232f607..f55ddeb652a3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -763,6 +763,9 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
ts->do_timer_last = 0;
}
+ /* Even if the tick was already stopped, load may have changed */
+ calc_load_nohz_start();
+
/* Skip reprogram of event if its not changed */
if (ts->tick_stopped && (expires == ts->next_tick)) {
/* Sanity check: make sure clockevent is actually programmed */
@@ -783,7 +786,6 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
* the scheduler tick in nohz_restart_sched_tick.
*/
if (!ts->tick_stopped) {
- calc_load_nohz_start();
quiet_vmstat();
ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
--
2.23.0
next reply other threads:[~2019-10-28 15:07 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 15:07 Frederic Weisbecker [this message]
2019-10-29 10:05 ` [PATCH] timers/nohz: Update nohz load even if tick already stopped Peter Zijlstra
2019-10-30 8:48 ` Scott Wood
2019-10-30 13:31 ` Peter Zijlstra
2019-11-01 5:11 ` Scott Wood
2019-11-04 22:17 ` Thomas Gleixner
2019-11-04 23:43 ` Thomas Gleixner
2019-11-05 7:30 ` Scott Wood
2019-11-05 9:53 ` Thomas Gleixner
2019-11-08 8:16 ` Scott Wood
2019-11-05 12:43 ` Peter Zijlstra
2019-11-06 8:37 ` Peter Zijlstra
2019-11-08 8:13 ` Scott Wood
2019-12-11 20:37 ` Scott Wood
2019-12-11 20:46 ` Scott Wood
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