lkml.org 
[lkml]   [2012]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3][0/6] memcg: prevent -ENOMEM in pre_destroy()
Hello, KAME.

On Fri, Jun 22, 2012 at 08:27:25AM +0900, Kamezawa Hiroyuki wrote:
> Remaining 20% of work is based on a modification to cgroup layer
>
> How do you think this patch ? (This patch is not tested yet...so
> may have troubles...) I think callers of pre_destory() is not so many...
>
> ==
> From a28db946f91f3509d25779e8c5db249506cc4b07 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Fri, 22 Jun 2012 08:38:38 +0900
> Subject: [PATCH] cgroup: keep cgroup_mutex() while calling ->pre_destroy()
>
> In past, memcg's pre_destroy() was verrry slow because of the possibility
> of page reclaiming in it. So, cgroup_mutex() was released before calling
> pre_destroy() callbacks. Now, it's enough fast. memcg just scans the list
> and move pages to other cgroup, no memory reclaim happens.
> Then, we can keep cgroup_mutex() there.
>
> By holding looks, we can avoid following cases
> 1. new task is attached while rmdir().
> 2. new child cgroup is created while rmdir()
> 3. new task is attached to cgroup and removed from cgroup before
> checking css's count. So, ->destroy() will be called even if
> some trashes by the task remains
>
> (3. is terrible case...even if I think it will not happen in real world..)

Ooh, once memcg drops the __DEPRECATED_clear_css_refs, cgroup_rmdir()
will mark the cgroup dead before start calling pre_destroy() and none
of the above will happen.

Thanks.

--
tejun


\
 
 \ /
  Last update: 2012-06-27 20:41    [W:0.054 / U:1.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site