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authorFrederic Weisbecker <fweisbec@gmail.com>2017-06-19 04:12:02 +0200
committerIngo Molnar <mingo@kernel.org>2017-06-22 11:30:02 +0200
commit387bc8b5536eeb0a92f4b4ab553539eaea2ac0ba (patch)
tree8c2069d1ac3f47a337e338b6425c565f24d92630 /kernel/sched
parenta0db971e4eb69fc84eb3d7ef94f718b483550b4a (diff)
sched/fair: Spare idle load balancing on nohz_full CPUs
Although idle load balancing obviously only concerns idle CPUs, it can be a disturbance on a busy nohz_full CPU. Indeed a CPU can only get rid of an idle load balancing duty once a tick fires while it runs a task and this can take a while on a nohz_full CPU. We could fix that and escape the idle load balancing duty from the very idle exit path but that would bring unecessary overhead. Lets just not bother and leave that job to housekeeping CPUs (those outside nohz_full range). The nohz_full CPUs simply don't want any disturbance. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1497838322-10913-4-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/fair.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a24661ac3d23..694c258b8771 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8683,6 +8683,10 @@ void nohz_balance_enter_idle(int cpu)
if (!cpu_active(cpu))
return;
+ /* Spare idle load balancing on CPUs that don't want to be disturbed: */
+ if (!is_housekeeping_cpu(cpu))
+ return;
+
if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
return;