linux-kernel - Re: [RFC] [PATCH 0/2] memcg: per cgroup dirty limit

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Date:	Mon, 22 Feb 2010 08:48:07 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrea Righi <arighi@...eler.com>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [PATCH 0/2] memcg: per cgroup dirty limit

On Sun, 21 Feb 2010 16:18:43 +0100
Andrea Righi <arighi@...eler.com> wrote:

> Control the maximum amount of dirty pages a cgroup can have at any given time.
> 
> Per cgroup dirty limit is like fixing the max amount of dirty (hard to reclaim)
> page cache used by any cgroup. So, in case of multiple cgroup writers, they
> will not be able to consume more than their designated share of dirty pages and
> will be forced to perform write-out if they cross that limit.
> 
> The overall design is the following:
> 
>  - account dirty pages per cgroup
>  - limit the number of dirty pages via memory.dirty_bytes in cgroupfs
>  - start to write-out in balance_dirty_pages() when the cgroup or global limit
>    is exceeded
> 
> This feature is supposed to be strictly connected to any underlying IO
> controller implementation, so we can stop increasing dirty pages in VM layer
> and enforce a write-out before any cgroup will consume the global amount of
> dirty pages defined by the /proc/sys/vm/dirty_ratio|dirty_bytes limit.
> 
> TODO:
>  - handle the migration of tasks across different cgroups (a page may be set
>    dirty when a task runs in a cgroup and cleared after the task is moved to
>    another cgroup).
>  - provide an appropriate documentation (in Documentation/cgroups/memory.txt)
> 

Thank you, this was a long concern in memcg.

Regards,
-Kame


> -Andrea
> 

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