sched/fair: Spare idle load balancing on nohz_full CPUs
authorFrederic Weisbecker <fweisbec@gmail.com>
Mon, 19 Jun 2017 02:12:02 +0000 (04:12 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 22 Jun 2017 09:30:02 +0000 (11:30 +0200)
commit387bc8b5536eeb0a92f4b4ab553539eaea2ac0ba
tree8c2069d1ac3f47a337e338b6425c565f24d92630
parenta0db971e4eb69fc84eb3d7ef94f718b483550b4a
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>
kernel/sched/fair.c