sched/nohz: Run NOHZ idle load balancer on HK_FLAG_MISC CPUs
authorNicholas Piggin <npiggin@gmail.com>
Fri, 12 Apr 2019 04:26:13 +0000 (14:26 +1000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 31 May 2019 13:46:14 +0000 (06:46 -0700)
commit07da741d48c40f09652d6556a196e0befbaf593a
tree21bd871f3cd4c0d25089cf850e1727f25f5ba646
parent216155aab5074c36a23a439a4dbd30ce20204bff
sched/nohz: Run NOHZ idle load balancer on HK_FLAG_MISC CPUs

[ Upstream commit 9b019acb72e4b5741d88e8936d6f200ed44b66b2 ]

The NOHZ idle balancer runs on the lowest idle CPU. This can
interfere with isolated CPUs, so confine it to HK_FLAG_MISC
housekeeping CPUs.

HK_FLAG_SCHED is not used for this because it is not set anywhere
at the moment. This could be folded into HK_FLAG_SCHED once that
option is fixed.

The problem was observed with increased jitter on an application
running on CPU0, caused by NOHZ idle load balancing being run on
CPU1 (an SMT sibling).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190412042613.28930-1-npiggin@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
kernel/sched/fair.c