[PATCH 04/10] memcg: disable local interrupts in lock_page_cgroup()

[KAMEZAWA Hiroyuki]

On Wed, 6 Oct 2010 09:15:34 +0900
Minchan Kim <minchan.kim at 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