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Sender: Tejun Heo <htejun@gmail.com>
Date:   Fri, 4 Jun 2021 08:45:19 -0400
From:   Tejun Heo <tj@kernel.org>
To:     Hillf Danton <hdanton@sina.com>
Cc:     Shakeel Butt <shakeelb@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Michal Hocko <mhocko@kernel.org>, Roman Gushchin <guro@fb.com>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        Huang Ying <ying.huang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] memcg: periodically flush the memcg stats
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References: <20210604015640.2586269-1-shakeelb@google.com>
 <20210604061816.3110-1-hdanton@sina.com>
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On Fri, Jun 04, 2021 at 02:18:16PM +0800, Hillf Danton wrote:
> On Thu,  3 Jun 2021 18:56:40 -0700 Shakeel Butt wrote:
> >  
> > +static void flush_memcg_stats(struct work_struct *w)
> > +{
> > +	cgroup_rstat_flush(root_mem_cgroup->css.cgroup);
> > +	schedule_delayed_work(&stats_flush, round_jiffies(2UL*HZ));
> > +}
> 
> Given flush may block, the unbound wq is what you need.
>
> 	queue_delayed_work(system_unbound_wq, &stats_flush, 2 * HZ);

Default per-cpu workqueue can block just fine. I don't see a strong reason
why this would need to be unbound.

-- 
tejun