Messages in this thread Patch in this message | | | From | Vlastimil Babka <> | Subject | [PATCH] mm, slab: reschedule cache_reap() on the same CPU | Date | Wed, 11 Apr 2018 09:00:07 +0200 |
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cache_reap() is initially scheduled in start_cpu_timer() via schedule_delayed_work_on(). But then the next iterations are scheduled via schedule_delayed_work(), i.e. using WORK_CPU_UNBOUND.
Thus since commit ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs") there is no guarantee the future iterations will run on the originally intended cpu, although it's still preferred. I was able to demonstrate this with /sys/module/workqueue/parameters/debug_force_rr_cpu. IIUC, it may also happen due to migrating timers in nohz context. As a result, some cpu's would be calling cache_reap() more frequently and others never.
This patch uses schedule_delayed_work_on() with the current cpu when scheduling the next iteration.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs") CC: <stable@vger.kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: David Rientjes <rientjes@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Christoph Lameter <cl@linux.com> Cc: Tejun Heo <tj@kernel.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> --- mm/slab.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/slab.c b/mm/slab.c index 9095c3945425..a76006aae857 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -4074,7 +4074,8 @@ static void cache_reap(struct work_struct *w) next_reap_node(); out: /* Set up the next iteration */ - schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_AC)); + schedule_delayed_work_on(smp_processor_id(), work, + round_jiffies_relative(REAPTIMEOUT_AC)); } void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo) -- 2.16.3
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