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

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Message-ID: <20171120094237.z6h3kx3ne5ld64pl@dhcp22.suse.cz>
Date:   Mon, 20 Nov 2017 10:42:37 +0100
From:   Michal Hocko <mhocko@...nel.org>
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>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Greg Thelen <gthelen@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

On Mon 20-11-17 01:33:09, Christoph Hellwig wrote:
> On Mon, Nov 20, 2017 at 10:25:26AM +0100, Michal Hocko wrote:
> > On Fri 17-11-17 09:35:21, Christoph Hellwig 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..
> > 
> > Davidlohr has tried that already http://lkml.kernel.org/r/1434398602.1903.15.camel@stgolabs.net
> > and failed. Doing SRCU inside core kernel is not seen with a great
> > support...
> 
> I can't actually find any objection in that thread.  What's the problem
> Davidlohr ran into?

The patch has been dropped because allnoconfig failed to compile back
then http://lkml.kernel.org/r/CAP=VYLr0rPWi1aeuk4w1On9CYRNmnEWwJgGtaX=wEvGaBURtrg@mail.gmail.com
I have problem to find the follow up discussion though. The main
argument was that SRC is not generally available and so the core
kernel should rely on it.
-- 
Michal Hocko SUSE Labs