[PATCH v3 4/6] sched/rt: Allow pulling unfitting task

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 4/6] sched/rt: Allow pulling unfitting task
Date: Mon,  2 Mar 2020 13:27:19 +0000	[thread overview]
Message-ID: <20200302132721.8353-5-qais.yousef@arm.com> (raw)
In-Reply-To: <20200302132721.8353-1-qais.yousef@arm.com>

When implemented RT Capacity Awareness; the logic was done such that if
a task was running on a fitting CPU, then it was sticky and we would try
our best to keep it there.

But as Steve suggested, to adhere to the strict priority rules of RT
class; allow pulling an RT task to unfitting CPU to ensure it gets a
chance to run ASAP.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware")
LINK: https://lore.kernel.org/lkml/20200203111451.0d1da58f@oasis.local.home/
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
---
 kernel/sched/rt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3071c8612c03..e79a23ad4a93 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1656,8 +1656,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
 {
 	if (!task_running(rq, p) &&
-	    cpumask_test_cpu(cpu, p->cpus_ptr) &&
-	    rt_task_fits_capacity(p, cpu))
+	    cpumask_test_cpu(cpu, p->cpus_ptr))
 		return 1;
 
 	return 0;
-- 
2.17.1

