linux-kernel - Re: [patch 2/2] mm: memcg: count pte references from every member of the reclaimed hierarchy

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Message-Id: <20120229120852.f2ca193e.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 29 Feb 2012 12:08:52 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/2] mm: memcg: count pte references from every member
 of the reclaimed hierarchy

On Wed, 29 Feb 2012 03:02:46 +0100
Johannes Weiner <hannes@...xchg.org> wrote:

> On Wed, Feb 29, 2012 at 09:39:46AM +0900, KAMEZAWA Hiroyuki wrote:
> > On Tue, 28 Feb 2012 15:14:49 +0100
> > Johannes Weiner <hannes@...xchg.org> wrote:
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -708,7 +708,8 @@ static enum page_references page_check_references(struct page *page,
> > >  	int referenced_ptes, referenced_page;
> > >  	unsigned long vm_flags;
> > >  
> > > -	referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
> > > +	referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
> > > +					  &vm_flags);
> > 
> > 
> > I'm sorry if I don't understand the codes... !sc->target_mem_cgroup case is handled ?
> 
> Yes, but it's not obvious from the diff alone.  page_referenced() does
> this:
> 
> 		/*
> 		 * If we are reclaiming on behalf of a cgroup, skip
> 		 * counting on behalf of references from different
> 		 * cgroups
> 		 */
> 		if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
> 			continue;
> 
> As a result, !sc->target_mem_cgroup -- global reclaim -- will never
> ignore references, or put differently, respect references from all
> memcgs, which is what we want.
> 
Ah, thank you. 

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

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