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From: Morten Rasmussen <morten.rasmussen@arm.com>
To: peterz@infradead.org, mingo@redhat.com
Cc: valentin.schneider@arm.com, dietmar.eggemann@arm.com,
	vincent.guittot@linaro.org, gaku.inami.xh@renesas.com,
	linux-kernel@vger.kernel.org,
	Morten Rasmussen <morten.rasmussen@arm.com>
Subject: [PATCHv2 4/7] sched/fair: Kick nohz balance if rq->misfit_task
Date: Thu, 15 Mar 2018 14:47:01 +0000	[thread overview]
Message-ID: <1521125224-15434-5-git-send-email-morten.rasmussen@arm.com> (raw)
In-Reply-To: <1521125224-15434-1-git-send-email-morten.rasmussen@arm.com>

From: Valentin Schneider <valentin.schneider@arm.com>

There already are a few conditions in nohz_kick_needed() to ensure
a nohz kick is triggered, but they are not enough for some misfit
task scenarios. Excluding asym packing, those are:

* rq->nr_running >=2: Not relevant here because we are running a
misfit task, it needs to be migrated regardless and potentially through
active balance.
* sds->nr_busy_cpus > 1: If there is only the misfit task being run
on a group of low capacity cpus, this will be evaluated to False.
* rq->cfs.h_nr_running >=1 && check_cpu_capacity(): Not relevant here,
misfit task needs to be migrated regardless of rt/IRQ pressure

As such, this commit adds an rq->misfit_task condition to trigger a
nohz kick.

The idea to kick a nohz balance for misfit tasks originally came from
Leo Yan <leo.yan@linaro.org>, and a similar patch was submitted for
the Android Common Kernel - see [1].

[1]: https://lists.linaro.org/pipermail/eas-dev/2016-September/000551.html

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
---
 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 496062860733..c791dd7ac9a8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9291,7 +9291,7 @@ static void nohz_balancer_kick(struct rq *rq)
 	if (time_before(now, nohz.next_balance))
 		goto out;
 
-	if (rq->nr_running >= 2) {
+	if (rq->nr_running >= 2 || rq->misfit_task_load) {
 		flags = NOHZ_KICK_MASK;
 		goto out;
 	}
-- 
2.7.4

  parent reply	other threads:[~2018-03-15 14:47 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-15 14:46 [PATCHv2 0/7] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Morten Rasmussen
2018-03-15 14:46 ` [PATCHv2 1/7] sched: Add static_key for asymmetric cpu capacity optimizations Morten Rasmussen
2018-04-27 14:04   ` [PATCHv2,1/7] " Jiada Wang
2018-04-29 19:09     ` Valentin Schneider
2018-03-15 14:46 ` [PATCHv2 2/7] sched/fair: Add group_misfit_task load-balance type Morten Rasmussen
2018-04-11 10:45   ` Peter Zijlstra
2018-03-15 14:47 ` [PATCHv2 3/7] sched/fair: Consider misfit tasks when load-balancing Morten Rasmussen
2018-04-11 10:46   ` Peter Zijlstra
2018-04-11 10:53   ` Peter Zijlstra
2018-03-15 14:47 ` Morten Rasmussen [this message]
2018-03-15 14:47 ` [PATCHv2 5/7] sched: Change root_domain->overload type to int Morten Rasmussen
2018-03-15 14:47 ` [PATCHv2 6/7] sched: Wrap rq->rd->overload accesses with READ/WRITE_ONCE Morten Rasmussen
2018-03-15 14:47 ` [PATCHv2 7/7] sched/fair: Set sd->overload when misfit Morten Rasmussen
2018-03-20  5:30 ` [PATCHv2 0/7] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Gaku Inami
2018-03-20  9:17   ` Morten Rasmussen

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