5.4-stable review patch. If anyone has any objections, please let me know.
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From: Valentin Schneider valentin.schneider@arm.com
[ Upstream commit 9ae7ab20b4835dbea0e5fc6a5c70171dc354a72e ]
As pointed out in commit
182a85f8a119 ("sched: Disable wakeup balancing")
SD_BALANCE_WAKE is a tad too aggressive, and is usually left unset.
However, it turns out cpuset domain relaxation will unconditionally set it on domains below the relaxation level. This made sense back when SD_BALANCE_WAKE was set unconditionally, but it no longer is the case.
We can improve things slightly by noticing that set_domain_attribute() is always called after sd_init(), so rather than setting flags we can rely on whatever sd_init() is doing and only clear certain flags when above the relaxation level.
While at it, slightly clean up the function and flip the relax level check to be more human readable.
Signed-off-by: Valentin Schneider valentin.schneider@arm.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: mingo@kernel.org Cc: vincent.guittot@linaro.org Cc: juri.lelli@redhat.com Cc: seto.hidetoshi@jp.fujitsu.com Cc: qperret@google.com Cc: Dietmar.Eggemann@arm.com Cc: morten.rasmussen@arm.com Link: https://lkml.kernel.org/r/20191014164408.32596-1-valentin.schneider@arm.com Stable-dep-of: a1fd0b9d751f ("sched/fair: Allow disabling sched_balance_newidle with sched_relax_domain_level") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/topology.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index e5ebaffc4fef5..844dc30fc5593 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1201,16 +1201,13 @@ static void set_domain_attribute(struct sched_domain *sd, if (!attr || attr->relax_domain_level < 0) { if (default_relax_domain_level < 0) return; - else - request = default_relax_domain_level; + request = default_relax_domain_level; } else request = attr->relax_domain_level; - if (request < sd->level) { + + if (sd->level > request) { /* Turn off idle balance on this domain: */ sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE); - } else { - /* Turn on idle balance on this domain: */ - sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE); } }