From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 7AD076B0007 for ; Tue, 3 Jul 2018 15:54:45 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id g9-v6so1445391wrq.7 for ; Tue, 03 Jul 2018 12:54:45 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 138-v6sor715090wmo.16.2018.07.03.12.54.44 for (Google Transport Security); Tue, 03 Jul 2018 12:54:44 -0700 (PDT) MIME-Version: 1.0 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> <20180703192517.GA22738@bombadil.infradead.org> In-Reply-To: <20180703192517.GA22738@bombadil.infradead.org> From: Shakeel Butt Date: Tue, 3 Jul 2018 12:54:31 -0700 Message-ID: Subject: Re: [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Kirill Tkhai , Vladimir Davydov , Alexander Viro , Johannes Weiner , Michal Hocko , Thomas Gleixner , Philippe Ombredanne , stummala@codeaurora.org, gregkh@linuxfoundation.org, Stephen Rothwell , Roman Gushchin , mka@chromium.org, Tetsuo Handa , Chris Wilson , longman@redhat.com, Minchan Kim , Huang Ying , Mel Gorman , jbacik@fb.com, Guenter Roeck , LKML , Linux MM , lirongqing@baidu.com, Andrey Ryabinin , Andrew Morton On Tue, Jul 3, 2018 at 12:25 PM Matthew Wilcox wrote: > > On Tue, Jul 03, 2018 at 12:19:35PM -0700, Shakeel Butt wrote: > > On Tue, Jul 3, 2018 at 12:13 PM Kirill Tkhai 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. I would say almost half. Sorry I do not have exact numbers. Basically we use ext4 very extensively and majority of shrinkers are related to ext4 (again I do not have exact numbers). One ext4 mount typically registers three shrinkers, one memcg-aware (sget) and two non-memcg aware (ext4_es_register_shrinker, ext4_xattr_create_cache). Shakeel