linux-kernel - Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

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Message-ID: <CALvZod5b8EBgJ=jTWfAs97zn3D9WPDP5j-2qAR5FGEYrn0GM6Q@mail.gmail.com>
Date:   Fri, 17 Nov 2017 09:53:22 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Minchan Kim <minchan@...nel.org>,
        Huang Ying <ying.huang@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Thelen <gthelen@...gle.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

On Fri, Nov 17, 2017 at 9:41 AM, Shakeel Butt <shakeelb@...gle.com> wrote:
> On Fri, Nov 17, 2017 at 9:35 AM, Christoph Hellwig <hch@...radead.org> wrote:
>> On Tue, Nov 14, 2017 at 06:37:42AM +0900, Tetsuo Handa wrote:
>>> Since do_shrink_slab() can reschedule, we cannot protect shrinker_list
>>> using one RCU section. But using atomic_inc()/atomic_dec() for each
>>> do_shrink_slab() call will not impact so much.
>>
>> But you could use SRCU..
>
> I looked into that but was advised to not go through that route due to
> SRCU behind the CONFIG_SRCU. However now I see the precedence of
> "#ifdef CONFIG_SRCU" in drivers/base/core.c and I think if we can take
> that route if even after Minchan's patch the issue persists.

Too many 'ifs' in the last sentence. I just wanted to say we can
consider SRCU if the issue persists even after Minchan's patch.