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| author |   Valentin Schneider <valentin.schneider@arm.com> | 2019-01-17 15:34:08 +0000 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2019-02-11 08:02:17 +0100 |
| commit | 892d59c22208be820a5463b5f74eb7f0b7f2b03a (patch) | |
| tree | 8df1c43462d3ac620487cb44f655bb0ae86d8bf1 /kernel/sched | |
| parent | sched/fair: Simplify nohz_balancer_kick() (diff) | |
| download | linux-dev-892d59c22208be820a5463b5f74eb7f0b7f2b03a.tar.xz linux-dev-892d59c22208be820a5463b5f74eb7f0b7f2b03a.zip | |
sched/fair: Explain LLC nohz kick condition
Provide a comment explaining the LLC related nohz kick in
nohz_balancer_kick().
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190117153411.2390-3-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0692c8ff6ff6..ac6b52d8c79e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9601,8 +9601,13 @@ static void nohz_balancer_kick(struct rq *rq) sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) { /* - * XXX: write a coherent comment on why we do this. - * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com + * If there is an imbalance between LLC domains (IOW we could + * increase the overall cache use), we need some less-loaded LLC + * domain to pull some load. Likewise, we may need to spread + * load within the current LLC domain (e.g. packed SMT cores but + * other CPUs are idle). We can't really know from here how busy + * the others are - so just get a nohz balance going if it looks + * like this LLC domain has tasks we could move. */ nr_busy = atomic_read(&sds->nr_busy_cpus); if (nr_busy > 1) { |