linux-kernel - Re: WARNINGs in set_task_reclaim_state with memory cgroupandfullmemory usage

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Message-ID: <20190827135322.GG7538@dhcp22.suse.cz>
Date:   Tue, 27 Aug 2019 15:53:22 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Yafang Shao <laoar.shao@...il.com>,
        Adric Blake <promarbler14@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: WARNINGs in set_task_reclaim_state with memory
 cgroupandfullmemory usage

On Tue 27-08-19 21:29:24, Hillf Danton wrote:
> 
> >> No preference seems in either way except for retaining
> >> nr_to_reclaim == SWAP_CLUSTER_MAX and target_mem_cgroup == memcg.
> >
> > Setting  target_mem_cgroup here may be a very subtle change for
> > subsequent processing.
> > Regarding retraining nr_to_reclaim == SWAP_CLUSTER_MAX, it may not
> > proper for direct reclaim, that may cause some stall if we iterate all
> > memcgs here.
> 
> Mind posting a RFC to collect thoughts?

I hope I have explained why this is not desirable
http://lkml.kernel.org/r/20190827120335.GA7538@dhcp22.suse.cz
-- 
Michal Hocko
SUSE Labs