linux-kernel - Re: [PATCH] mark_page_accessed() in do_swap

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Message-Id: <20090115201224.676928d6.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 15 Jan 2009 20:12:24 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	balbir@...ux.vnet.ibm.com,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	lizf@...fujitsu.com, menage@...gle.com,
	Hugh Dickins <hugh@...itas.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mark_page_accessed() in do_swap_page() move latter than
 memcg charge

On Thu, 15 Jan 2009 20:08:36 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> 
> sorry for late responce.
> 
> > > In this case we've hit a case where the page is valid and the pc is
> > > not. This does fix the problem, but won't this impact us getting
> > > correct reclaim stats and thus indirectly impact the working of
> > > pressure?
> > > 
> >  - If retruns NULL, only global LRU's status is updated. 
> > 
> > Because this page is not belongs to any memcg, we cannot update
> > any counters. But yes, your point is a concern.
> > 
> > Maybe moving acitvate_page() to
> > ==
> > do_swap_page()
> > {
> >     
> > - activate_page()
> >    mem_cgroup_try_charge()..
> >    ....
> >    mem_cgroup_commit_charge()....
> >    ....
> > +  activate_page()   
> > }
> > ==
> > is necessary. How do you think, kosaki ?
> 
> 
> OK. it makes sense. and my test found no bug.
> 
Thank you very much! KOSAKI.

Reviewed-by; KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

-Kame

> ==
> 
> mark_page_accessed() update reclaim_stat statics.
> but currently, memcg charge is called after mark_page_accessed().
> 
> then, mark_page_accessed() don't update memcg statics correctly.
> 
> fixing here.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
> 
> ---
>  mm/memory.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Index: b/mm/memory.c
> ===================================================================
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2426,8 +2426,6 @@ static int do_swap_page(struct mm_struct
>  		count_vm_event(PGMAJFAULT);
>  	}
>  
> -	mark_page_accessed(page);
> -
>  	lock_page(page);
>  	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
>  
> @@ -2480,6 +2478,8 @@ static int do_swap_page(struct mm_struct
>  		try_to_free_swap(page);
>  	unlock_page(page);
>  
> +	mark_page_accessed(page);
> +
>  	if (write_access) {
>  		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
>  		if (ret & VM_FAULT_ERROR)
> 
> 
> 
> 

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