From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197])
	by kanga.kvack.org (Postfix) with ESMTP id 7D2686B000A
	for <linux-mm@kvack.org>; Tue,  3 Jul 2018 15:26:03 -0400 (EDT)
Received: by mail-pf0-f197.google.com with SMTP id l2-v6so1495969pff.3
        for <linux-mm@kvack.org>; Tue, 03 Jul 2018 12:26:03 -0700 (PDT)
Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133])
        by mx.google.com with ESMTPS id g38-v6si1736077plb.262.2018.07.03.12.26.02
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256);
        Tue, 03 Jul 2018 12:26:02 -0700 (PDT)
Date: Tue, 3 Jul 2018 12:25:17 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker
Message-ID: <20180703192517.GA22738@bombadil.infradead.org>
References: <153063036670.1818.16010062622751502.stgit@localhost.localdomain>
 <153063054586.1818.6041047871606697364.stgit@localhost.localdomain>
 <20180703152723.GB21590@bombadil.infradead.org>
 <2d845a0d-d147-7250-747e-27e493b6a627@virtuozzo.com>
 <20180703175808.GC4834@bombadil.infradead.org>
 <94c282fd-1b5a-e959-b344-01a51fd5fc2e@virtuozzo.com>
 <CALvZod7v4n62PVvC50VSNV12ZV0WdsY4GOQt68EmY4u5fc9hfQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALvZod7v4n62PVvC50VSNV12ZV0WdsY4GOQt68EmY4u5fc9hfQ@mail.gmail.com>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Shakeel Butt <shakeelb@google.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>, Vladimir Davydov <vdavydov.dev@gmail.com>, Alexander Viro <viro@zeniv.linux.org.uk>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Philippe Ombredanne <pombredanne@nexb.com>, stummala@codeaurora.org, gregkh@linuxfoundation.org, Stephen Rothwell <sfr@canb.auug.org.au>, Roman Gushchin <guro@fb.com>, mka@chromium.org, Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>, Chris Wilson <chris@chris-wilson.co.uk>, longman@redhat.com, Minchan Kim <minchan@kernel.org>, Huang Ying <ying.huang@intel.com>, Mel Gorman <mgorman@techsingularity.net>, jbacik@fb.com, Guenter Roeck <linux@roeck-us.net>, LKML <linux-kernel@vger.kernel.org>, Linux MM <linux-mm@kvack.org>, lirongqing@baidu.com, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>

On Tue, Jul 03, 2018 at 12:19:35PM -0700, Shakeel Butt wrote:
> On Tue, Jul 3, 2018 at 12:13 PM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
> > > Do we really have so very many !memcg-aware shrinkers?
> > >
> > > $ git grep -w register_shrinker |wc
> > >      32     119    2221
> > > $ git grep -w register_shrinker_prepared |wc
> > >       4      13     268
> > > (that's an overstatement; one of those is the declaration, one the definition,
> > > and one an internal call, so we actually only have one caller of _prepared).
> > >
> > > So it looks to me like your average system has one shrinker per
> > > filesystem, one per graphics card, one per raid5 device, and a few
> > > miscellaneous.  I'd be shocked if anybody had more than 100 shrinkers
> > > registered on their laptop.
> > >
> > > I think we should err on the side of simiplicity and just have one IDR for
> > > every shrinker instead of playing games to solve a theoretical problem.
> >
> > It just a standard situation for the systems with many containers. Every mount
> > introduce a new shrinker to the system, so it's easy to see a system with
> > 100 or ever 1000 shrinkers. AFAIR, Shakeel said he also has the similar
> > configurations.
> >
> 
> I can say on our production systems, a couple thousand shrinkers is normal.

But how many are !memcg aware?  It sounds to me like almost all of the
shrinkers come through the sget_userns() caller, so the other shrinkers
are almost irrelevant.