[tip:timers/nohz] nohz: Set isolcpus when nohz_full is set

[tip-bot for Chris Metcalf]

Commit-ID:  8cb9764fc88b41db11f251e8b2a0d006578b7eb4
Gitweb:     http://git.kernel.org/tip/8cb9764fc88b41db11f251e8b2a0d006578b7eb4
Author:     Chris Metcalf <cmetcalf@xxxxxxxxxx>
AuthorDate: Wed, 6 May 2015 18:04:26 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 7 May 2015 12:02:51 +0200

nohz: Set isolcpus when nohz_full is set

nohz_full is only useful with isolcpus are also set, since
otherwise the scheduler has to run periodically to try to
determine whether to steal work from other cores.

Accordingly, when booting with nohz_full=xxx on the command
line, we should act as if isolcpus=xxx was also set, and set
(or extend) the isolcpus set to include the nohz_full cpus.

Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1430928266-24888-5-git-send-email-fweisbec@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 54f032c..b8f4876 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7036,6 +7036,9 @@ void __init sched_init_smp(void)
 	alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
 	alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
 
+	/* nohz_full won't take effect without isolating the cpus. */
+	tick_nohz_full_add_cpus_to(cpu_isolated_map);
+
 	sched_init_numa();
 
 	/*
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/