linux-kernel - Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8)

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Date:	Wed, 28 May 2008 10:12:29 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	Rik van Riel <riel@...hat.com>, balbir@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kosaki Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH -mm 00/16] VM pageout scalability improvements (V8)

On Tue, 27 May 2008 11:54:02 -0400
Lee Schermerhorn <Lee.Schermerhorn@...com> wrote:

> Since Balbir is starting to look at this, I need to ask about
> interaction with the memory controller.  It is currently unaware of the
> noreclaim list.  I'm not sure what will happen if/when the memory
> controller tries to reclaim a page that system has moved to the
> noreclaim list.  Something we'll need to address.  It's on my list, but
> I won't get to it for a couple of weeks.
> 
In my understanding, 2 checks we have to do.

1. When memcg finds PG_noreclaim page in its LRU, move it to noreclaim list of
   memcg.
2. When PG_noreclaim page is moved back to generic LRU, memcg should move
   it on its list. (we have to add a hook somewhere.)

But this may break current 'loose' synchronization between global LRU and
memcg's LRU. When PG_noreclaim page is put back into active/inactive LRU ?

concerns are
A. how to implement '2'
B. race condtions.

But maybe we don't have to write a big patch.

Thanks,
-Kame

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