From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 3EFFD6B0003 for ; Tue, 3 Jul 2018 15:13:06 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id p184-v6so3346777qkc.15 for ; Tue, 03 Jul 2018 12:13:06 -0700 (PDT) Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0095.outbound.protection.outlook.com. [104.47.0.95]) by mx.google.com with ESMTPS id l87-v6si667279qki.360.2018.07.03.12.13.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 03 Jul 2018 12:13:04 -0700 (PDT) Subject: Re: [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker 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> From: Kirill Tkhai Message-ID: <94c282fd-1b5a-e959-b344-01a51fd5fc2e@virtuozzo.com> Date: Tue, 3 Jul 2018 22:12:47 +0300 MIME-Version: 1.0 In-Reply-To: <20180703175808.GC4834@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: vdavydov.dev@gmail.com, shakeelb@google.com, viro@zeniv.linux.org.uk, hannes@cmpxchg.org, mhocko@kernel.org, tglx@linutronix.de, pombredanne@nexb.com, stummala@codeaurora.org, gregkh@linuxfoundation.org, sfr@canb.auug.org.au, guro@fb.com, mka@chromium.org, penguin-kernel@I-love.SAKURA.ne.jp, chris@chris-wilson.co.uk, longman@redhat.com, minchan@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, jbacik@fb.com, linux@roeck-us.net, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lirongqing@baidu.com, aryabinin@virtuozzo.com, akpm@linux-foundation.org On 03.07.2018 20:58, Matthew Wilcox wrote: > On Tue, Jul 03, 2018 at 06:46:57PM +0300, Kirill Tkhai wrote: >> shrinker_idr now contains only memcg-aware shrinkers, so all bits from memcg map >> may be potentially populated. In case of memcg-aware shrinkers and !memcg-aware >> shrinkers share the same numbers like you suggest, this will lead to increasing >> size of memcg maps, which is bad for memory consumption. So, memcg-aware shrinkers >> should to have its own IDR and its own numbers. The tricks like allocation big >> IDs for !memcg-aware shrinkers seem bad for me, since they make the code more >> complicated. > > 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. So, this problem is not theoretical, it's just a standard situation for active consumer or Docker/etc. >>> This will actually reduce the size of each shrinker and be more >>> cache-efficient when calling the shrinkers. I think we can also get >>> rid of the shrinker_rwsem eventually, but let's leave it for now. >> >> This patchset does not make the cache-efficient bad, since without the patchset the situation >> is so bad, that it's just impossible to talk about the cache efficiently, >> so let's leave lockless iteration/etc for the future works. > > The situation is that bad /for your use case/. Not so much for others. > You're introducing additional complexity here, and it'd be nice if we > can remove some of the complexity that's already there. You started from cache-efficienty, and now you moved to existing complexity. I did some cleanups in this patchset, also there is Vladimir's patch, which simplifies shrinker logic. Also there is already 17 patches. Which already existing complexity you want to remove? I don't think there is existing complexity directly connected to this patchset.