linux-kernel - [PATCH 2/2] nohz: make nohz

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Message-ID: <1428078248-5425-2-git-send-email-cmetcalf@ezchip.com>
Date:	Fri, 3 Apr 2015 12:24:08 -0400
From:	<cmetcalf@...hip.com>
To:	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
CC:	Chris Metcalf <cmetcalf@...hip.com>
Subject: [PATCH 2/2] nohz: make nohz_full imply isolcpus

From: Chris Metcalf <cmetcalf@...hip.com>

It's not clear that nohz_full is useful without isolcpus also
set, since otherwise the scheduler has to run periodically to
try to determine whether to steal work from other cores.

Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
---
I am puzzled why this has not been done before, so I suspect
there is some argument against it that I am missing, but I
wasn't able to turn anything up by searching LKML.

 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f0f831e8a345..275f12c608f2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6836,6 +6836,7 @@ static int init_sched_domains(const struct cpumask *cpu_map)
 	doms_cur = alloc_sched_domains(ndoms_cur);
 	if (!doms_cur)
 		doms_cur = &fallback_doms;
+	tick_nohz_full_set_cpus(cpu_isolated_map);
 	cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
 	err = build_sched_domains(doms_cur[0], NULL);
 	register_sched_domain_sysctl();
-- 
2.1.2

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