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Date: Thu, 7 Oct 2010 09:35:45 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Subject: Re: [PATCH 04/10] memcg: disable local interrupts in
 lock_page_cgroup()
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On Wed, 6 Oct 2010 09:15:34 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:

> First of all, we could add your patch as it is and I don't expect any
> regression report about interrupt latency.
> That's because many embedded guys doesn't use mmotm and have a
> tendency to not report regression of VM.
> Even they don't use memcg. Hmm...
> 
> I pass the decision to MAINTAINER Kame and Balbir.
> Thanks for the detail explanation.
> 

Hmm. IRQ delay is a concern. So, my option is this. How do you think ?

1. remove local_irq_save()/restore() in lock/unlock_page_cgroup().
   yes, I don't like it.

2. At moving charge, do this:
	a) lock_page()/ or trylock_page()
	b) wait_on_page_writeback()
	c) do move_account under lock_page_cgroup().
	c) unlock_page()


Then, Writeback updates will never come from IRQ context while
lock/unlock_page_cgroup() is held by move_account(). There will be no race.

Do I miss something ?

Thanks,
-Kame