Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Pekka Enberg <penberg@iki.fi>
To: Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	David Rientjes <rientjes@google.com>,
	Pekka Enberg <penberg@kernel.org>,
	Christoph Lameter <cl@linux.com>, Tejun Heo <tj@kernel.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Stephen Boyd <sboyd@kernel.org>
Subject: Re: [PATCH] mm, slab: reschedule cache_reap() on the same CPU
Date: Wed, 11 Apr 2018 13:53:12 +0300
Message-ID: <71010251-e1bc-e934-cecf-ae37a1cede90@iki.fi> (raw)
In-Reply-To: <20180411070007.32225-1-vbabka@suse.cz>



On 11/04/2018 10.00, Vlastimil Babka wrote:
> 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>

Acked-by: Pekka Enberg <penberg@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)
> 

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-10  8:15 [RFC] " Vlastimil Babka
2018-04-10 14:12 ` Christopher Lameter
2018-04-10 14:17   ` Tejun Heo
2018-04-10 19:40   ` Vlastimil Babka
2018-04-10 19:53     ` Tejun Heo
2018-04-10 20:13       ` Vlastimil Babka
2018-04-10 20:23         ` Tejun Heo
2018-04-11  7:00 ` [PATCH] " Vlastimil Babka
2018-04-11 10:53   ` Pekka Enberg [this message]
2018-04-11 13:41     ` Christopher Lameter
2018-04-12  0:47   ` Minchan Kim
2018-04-13  8:44     ` Vlastimil Babka

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=71010251-e1bc-e934-cecf-ae37a1cede90@iki.fi \
    --to=penberg@iki.fi \
    --cc=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=jiangshanlai@gmail.com \
    --cc=john.stultz@linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=sboyd@kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=tj@kernel.org \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git