From: Qais Yousef <qais.yousef@arm.com>
To: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Pavan Kondeti <pkondeti@codeaurora.org>
Cc: Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel@vger.kernel.org, Qais Yousef <qais.yousef@arm.com>
Subject: [PATCH v3 5/6] sched/rt: Remove unnecessary push for unfit tasks
Date: Mon, 2 Mar 2020 13:27:20 +0000 [thread overview]
Message-ID: <20200302132721.8353-6-qais.yousef@arm.com> (raw)
In-Reply-To: <20200302132721.8353-1-qais.yousef@arm.com>
In task_woken_rt() and switched_to_rto() we try trigger push-pull if the
task is unfit.
But the logic is found lacking because if the task was the only one
running on the CPU, then rt_rq is not in overloaded state and won't
trigger a push.
The necessity of this logic was under a debate as well, a summary of
the discussion can be found in the following thread.
https://lore.kernel.org/lkml/20200226160247.iqvdakiqbakk2llz@e107158-lin.cambridge.arm.com/
Remove the logic for now until a better approach is agreed upon.
Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
---
kernel/sched/rt.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e79a23ad4a93..ce230bec6847 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2225,7 +2225,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
(rq->curr->nr_cpus_allowed < 2 ||
rq->curr->prio <= p->prio);
- if (need_to_push || !rt_task_fits_capacity(p, cpu_of(rq)))
+ if (need_to_push)
push_rt_tasks(rq);
}
@@ -2297,10 +2297,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
*/
if (task_on_rq_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
- bool need_to_push = rq->rt.overloaded ||
- !rt_task_fits_capacity(p, cpu_of(rq));
-
- if (p->nr_cpus_allowed > 1 && need_to_push)
+ if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
rt_queue_push_tasks(rq);
#endif /* CONFIG_SMP */
if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
--
2.17.1
next prev parent reply other threads:[~2020-03-02 13:27 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-02 13:27 [PATCH v3 0/6] RT Capacity Awareness Fixes & Improvements Qais Yousef
2020-03-02 13:27 ` [PATCH v3 1/6] sched/rt: cpupri_find: Implement fallback mechanism for !fit case Qais Yousef
[not found] ` <20200304143200.GA13200@geo.homenetwork>
2020-03-04 15:18 ` Qais Yousef
2020-03-04 16:27 ` Steven Rostedt
2020-03-04 17:39 ` Qais Yousef
2020-03-04 18:54 ` Steven Rostedt
2020-03-04 20:01 ` Qais Yousef
2020-03-05 12:43 ` Qais Yousef
2020-03-10 14:22 ` Qais Yousef
2020-03-11 13:51 ` Steven Rostedt
2020-03-20 12:58 ` [tip: sched/core] sched/rt: cpupri_find: Trigger a full search as fallback tip-bot2 for Qais Yousef
2020-03-06 14:42 ` [tip: sched/core] sched/rt: cpupri_find: Implement fallback mechanism for !fit case tip-bot2 for Qais Yousef
2020-03-02 13:27 ` [PATCH v3 2/6] sched/rt: Re-instate old behavior in select_task_rq_rt Qais Yousef
2020-03-06 14:42 ` [tip: sched/core] sched/rt: Re-instate old behavior in select_task_rq_rt() tip-bot2 for Qais Yousef
2020-03-02 13:27 ` [PATCH v3 3/6] sched/rt: Optimize cpupri_find on non-heterogenous systems Qais Yousef
2020-03-06 14:42 ` [tip: sched/core] sched/rt: Optimize cpupri_find() " tip-bot2 for Qais Yousef
2020-03-02 13:27 ` [PATCH v3 4/6] sched/rt: Allow pulling unfitting task Qais Yousef
[not found] ` <20200304145219.GA14173@geo.homenetwork>
2020-03-04 15:28 ` Qais Yousef
2020-03-06 14:42 ` [tip: sched/core] " tip-bot2 for Qais Yousef
2020-03-02 13:27 ` Qais Yousef [this message]
2020-03-06 14:42 ` [tip: sched/core] sched/rt: Remove unnecessary push for unfit tasks tip-bot2 for Qais Yousef
2020-03-02 13:27 ` [PATCH v3 6/6] sched/rt: Fix pushing unfit tasks to a better CPU Qais Yousef
2020-03-06 17:51 ` Qais Yousef
2020-03-11 10:53 ` Pavan Kondeti
2020-03-11 14:11 ` Qais Yousef
2020-03-11 14:00 ` Steven Rostedt
2020-03-11 14:23 ` Qais Yousef
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