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From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@kernel.org>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	cgroups@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] memcg: Remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure
Date: Wed, 1 Aug 2018 19:16:26 +0300	[thread overview]
Message-ID: <20180801161626.j2575eru2x3lukfj@esperanza> (raw)
In-Reply-To: <20180730153113.GB4567@cmpxchg.org>

On Mon, Jul 30, 2018 at 11:31:13AM -0400, Johannes Weiner wrote:
> On Sun, Jul 29, 2018 at 10:26:21PM +0300, Vladimir Davydov wrote:
> > On Fri, Jul 27, 2018 at 03:31:34PM -0400, Johannes Weiner wrote:
> > > That said, the lifetime of the root reference on the ID is the online
> > > state, we put that in css_offline. Is there a reason we need to have
> > > the ID ready and the memcg in the IDR before onlining it?
> > 
> > I fail to see any reason for this in the code.
> 
> Me neither, thanks for double checking.
> 
> The patch also survives stress testing cgroup creation and destruction
> with the script from 73f576c04b94 ("mm: memcontrol: fix cgroup
> creation failure after many small jobs").
> 
> > > Can we do something like this and not mess with the alloc/free
> > > sequence at all?
> > 
> > I guess so, and this definitely looks better to me.
> 
> Cool, then I think we should merge Kirill's patch as the fix and mine
> as a follow-up cleanup.
> 
> ---
> 
> From b4106ea1f163479da805eceada60c942bd66e524 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@cmpxchg.org>
> Date: Mon, 30 Jul 2018 11:03:55 -0400
> Subject: [PATCH] mm: memcontrol: simplify memcg idr allocation and error
>  unwinding
> 
> The memcg ID is allocated early in the multi-step memcg creation
> process, which needs 2-step ID allocation and IDR publishing, as well
> as two separate IDR cleanup/unwind sites on error.
> 
> Defer the IDR allocation until the last second during onlining to
> eliminate all this complexity. There is no requirement to have the ID
> and IDR entry earlier than that. And the root reference to the ID is
> put in the offline path, so this matches nicely.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>

      parent reply	other threads:[~2018-08-01 16:16 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-12 14:52 [PATCH] memcg: Remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure Kirill Tkhai
2018-04-13  8:55 ` Michal Hocko
2018-04-13  9:35   ` Kirill Tkhai
2018-04-13 11:02     ` Michal Hocko
2018-04-13 11:06       ` Kirill Tkhai
2018-04-13 11:20         ` Michal Hocko
2018-04-13 11:29           ` Kirill Tkhai
2018-04-13 11:38             ` Michal Hocko
2018-04-13 11:49               ` Kirill Tkhai
2018-04-13 11:54                 ` Michal Hocko
2018-04-13 12:07                   ` Kirill Tkhai
2018-04-13 12:14                     ` Michal Hocko
2018-04-13 12:51                       ` Michal Hocko
2018-07-26 23:25                         ` Andrew Morton
2018-07-27 19:31                           ` Johannes Weiner
2018-07-29 19:26                             ` Vladimir Davydov
2018-07-30 15:31                               ` Johannes Weiner
2018-07-31 23:39                                 ` Andrew Morton
2018-08-01 15:55                                   ` Johannes Weiner
2018-08-01 16:22                                     ` Vladimir Davydov
2018-08-02  8:03                                       ` Kirill Tkhai
2018-08-02  8:13                                         ` [PATCH] memcg: Add comment to mem_cgroup_css_online() Kirill Tkhai
2018-08-01 16:16                                 ` Vladimir Davydov [this message]

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