linux-kernel - Re: [PATCH] mm/slab: fix kmemcg cache creation delayed issue

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Message-ID: <20161007082055.GH18439@dhcp22.suse.cz>
Date:   Fri, 7 Oct 2016 10:20:55 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Doug Smythies <dsmythies@...us.net>,
        'Andrew Morton' <akpm@...ux-foundation.org>,
        'Christoph Lameter' <cl@...ux.com>,
        'Pekka Enberg' <penberg@...nel.org>,
        'David Rientjes' <rientjes@...gle.com>,
        'Johannes Weiner' <hannes@...xchg.org>,
        'Vladimir Davydov' <vdavydov.dev@...il.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm/slab: fix kmemcg cache creation delayed issue

On Fri 07-10-16 14:14:01, Joonsoo Kim wrote:
> On Thu, Oct 06, 2016 at 09:02:00AM -0700, Doug Smythies wrote:
> > It was my (limited) understanding that the subsequent 2 patch set
> > superseded this patch. Indeed, the 2 patch set seems to solve
> > both the SLAB and SLUB bug reports.
> 
> It would mean that patch 1 solves both the SLAB and SLUB bug reports
> since patch 2 is only effective for SLUB.
> 
> Reason that I send this patch is that although patch 1 fixes the
> issue that too many kworkers are created, kmem_cache creation/destory
> is still slowed by synchronize_sched() and it would cause kmemcg
> usage counting delayed. I'm not sure how bad it is but it's generally
> better to start accounting as soon as possible. With patch 2 for SLUB
> and this patch for SLAB, performance of kmem_cache
> creation/destory would recover.

OK, so do we really want/need it for stable as well. I am not opposing
that but the effect doesn't seem to be a clear cut.
-- 
Michal Hocko
SUSE Labs