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

From: Michal Hocko <mhocko@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	Minchan Kim <minchan@kernel.org>,
	Huang Ying <ying.huang@intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shakeel Butt <shakeelb@google.com>,
	Greg Thelen <gthelen@google.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.
Date: Mon, 20 Nov 2017 10:42:37 +0100	[thread overview]
Message-ID: <20171120094237.z6h3kx3ne5ld64pl@dhcp22.suse.cz> (raw)
In-Reply-To: <20171120093309.GA19627@infradead.org>

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