From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id 5E1086B000A for ; Mon, 14 May 2018 23:29:15 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id y17-v6so3855891lfj.19 for ; Mon, 14 May 2018 20:29:15 -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 h84-v6sor2391576lfl.97.2018.05.14.20.29.13 for (Google Transport Security); Mon, 14 May 2018 20:29:13 -0700 (PDT) Date: Tue, 15 May 2018 06:29:09 +0300 From: Vladimir Davydov Subject: Re: [PATCH v5 01/13] mm: Assign id to every memcg-aware shrinker Message-ID: <20180515032909.kjbhxxg7463nnvwo@esperanza> References: <152594582808.22949.8353313986092337675.stgit@localhost.localdomain> <152594593798.22949.6730606876057040426.stgit@localhost.localdomain> <20180513051509.df2tcmbhxn3q2fp7@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Kirill Tkhai Cc: akpm@linux-foundation.org, 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, willy@infradead.org, lirongqing@baidu.com, aryabinin@virtuozzo.com On Mon, May 14, 2018 at 12:03:38PM +0300, Kirill Tkhai wrote: > On 13.05.2018 08:15, Vladimir Davydov wrote: > > On Thu, May 10, 2018 at 12:52:18PM +0300, Kirill Tkhai wrote: > >> The patch introduces shrinker::id number, which is used to enumerate > >> memcg-aware shrinkers. The number start from 0, and the code tries > >> to maintain it as small as possible. > >> > >> This will be used as to represent a memcg-aware shrinkers in memcg > >> shrinkers map. > >> > >> Since all memcg-aware shrinkers are based on list_lru, which is per-memcg > >> in case of !SLOB only, the new functionality will be under MEMCG && !SLOB > >> ifdef (symlinked to CONFIG_MEMCG_SHRINKER). > > > > Using MEMCG && !SLOB instead of introducing a new config option was done > > deliberately, see: > > > > http://lkml.kernel.org/r/20151210202244.GA4809@cmpxchg.org > > > > I guess, this doesn't work well any more, as there are more and more > > parts depending on kmem accounting, like shrinkers. If you really want > > to introduce a new option, I think you should call it CONFIG_MEMCG_KMEM > > and use it consistently throughout the code instead of MEMCG && !SLOB. > > And this should be done in a separate patch. > > What do you mean under "consistently throughout the code"? Should I replace > all MEMCG && !SLOB with CONFIG_MEMCG_KMEM over existing code? Yes, otherwise it looks messy - in some places we check !SLOB, in others we use CONFIG_MEMCG_SHRINKER (or whatever it will be called). > > >> diff --git a/fs/super.c b/fs/super.c > >> index 122c402049a2..16c153d2f4f1 100644 > >> --- a/fs/super.c > >> +++ b/fs/super.c > >> @@ -248,6 +248,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags, > >> s->s_time_gran = 1000000000; > >> s->cleancache_poolid = CLEANCACHE_NO_POOL; > >> > >> +#ifdef CONFIG_MEMCG_SHRINKER > >> + s->s_shrink.id = -1; > >> +#endif > > > > No point doing that - you are going to overwrite the id anyway in > > prealloc_shrinker(). > > Not so, this is done deliberately. alloc_super() has the only "fail" label, > and it handles all the allocation errors there. The patch just behaves in > the same style. It sets "-1" to make destroy_unused_super() able to differ > the cases, when shrinker is really initialized, and when it's not. > If you don't like this, I can move "s->s_shrink.id = -1;" into > prealloc_memcg_shrinker() instead of this. Yes, please do so that we don't have MEMCG ifdefs in fs code. Thanks.