linux-kernel - Re: [RFI] Shared accounting for memory resource controller

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Date:	Wed, 8 Apr 2009 14:19:52 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"lizf@...fujitsu.com" <lizf@...fujitsu.com>,
	Rik van Riel <riel@...riel.com>,
	Bharata B Rao <bharata.rao@...ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFI] Shared accounting for memory resource controller

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-04-08 17:03:41]:

> On Wed, 8 Apr 2009 13:18:09 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
> > > > 3. Using the above, we can then try to (using an algorithm you
> > > > proposed), try to do some work for figuring out the shared percentage.
> > > > 
> > > This is the point. At last. Why "# of shared pages" is important ?
> > > 
> > 
> > I posted this in my motivation yesterday. # of shared pages can help
> > plan the system better and the size of the cgroup. A cgroup might have
> > small usage_in_bytes but large number of shared pages. We need a
> > metric that can help figure out the fair usage of the cgroup.
> > 
> I don't fully understand but NR_FILE_MAPPED is an information in /proc/meminfo.
> I personally think I want to support information in /proc/meminfo per memcg.
> 
> Hmm ? then, if you add a hook, it seems
> == mm/rmap.c
>  689 void page_add_file_rmap(struct page *page)
>  690 {
>  691         if (atomic_inc_and_test(&page->_mapcount))
>  692                 __inc_zone_page_state(page, NR_FILE_MAPPED);
>  693 }
> ==  page_remove_rmap(struct page *page)
>  739                 __dec_zone_page_state(page,
>  740                         PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
> ==
> 
> Is good place to go, maybe.
> 
> page->page_cgroup->mem_cgroup-> inc/dec counter ?
> 
> Maybe the patch itself will be simple, overhead is unknown..

I thought of the same thing, but then moved to the following

... mem_cgroup_charge_statistics(..) {
 if (page_mapcount(page) == 0 && page_is_file_cache(page))
    __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_FILE_RSS, val);

But I've not yet tested the end result


-- 
	Balbir
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