[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20120322142941.01e601c0.akpm@linux-foundation.org>
Date: Thu, 22 Mar 2012 14:29:41 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux Kernel <linux-kernel@...r.kernel.org>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
Hugh Dickins <hughd@...gle.com>,
"n-horiguchi@...jp.nec.com" <n-horiguchi@...jp.nec.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Glauber Costa <glommer@...allels.com>
Subject: Re: [PATCH] memcg: change behavior of moving charges at task move
On Wed, 21 Mar 2012 18:52:04 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> As discussed before, I post this to fix the spec and implementation of task moving.
> Then, do you think what target kernel version should be ? 3.4/3.5 ?
> but yes, it may be late for 3.4....
Well, the key information here is "what effect does the bug have upon
users".
> In documentation, it's said that 'shared anon are not moved'.
> But in implementation, the check was wrong.
>
> if (!move_anon() || page_mapcount(page) > 2)
>
> Ah, memcg has been moving shared anon pages for a long time.
>
> Then, here is a discussion about handling of shared anon pages.
>
> - It's complex
> - Now, shared file caches are moved in force.
> - It adds unclear check as page_mapcount(). To do correct check,
> we should check swap users, etc.
> - No one notice this implementation behavior. So, no one get benefit
> from the design.
> - In general, once task is moved to a cgroup for running, it will not
> be moved....
> - Finally, we have control knob as memory.move_charge_at_immigrate.
>
> Here is a patch to allow moving shared pages, completely. This makes
> memcg simpler and fix current broken code.
>
> Note:
> IIUC, libcgroup's cgroup daemon moves tasks after exec().
> So, it's not affected.
> libcgroup's command "cgexec" does move itsef to a memcg and call exec()
> without fork(). it's not affected.
>
> Changelog:
> - fixed PageAnon() check.
> - remove call of lookup_swap_cache()
> - fixed Documentation.
But you forgot to tell us :(
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists