linux-kernel - Re: [PATCH 03/10] soft-offline: use migrate_pages() instead of migrate_huge

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Message-ID: <20130329093624.GC21227@dhcp22.suse.cz>
Date:	Fri, 29 Mar 2013 10:36:24 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10] soft-offline: use migrate_pages() instead of
 migrate_huge_page()

On Fri 29-03-13 10:56:00, Aneesh Kumar K.V wrote:
> Michal Hocko <mhocko@...e.cz> writes:
[...]
> > Little bit offtopic:
> > Btw. hugetlb migration breaks to charging even before this patchset
> > AFAICS. The above put_page should remove the last reference and then it
> > will uncharge it but I do not see anything that would charge a new page.
> > This is all because regula LRU pages are uncharged when they are
> > unmapped. But this a different story not related to this series.
> 
> 
> But when we call that put_page, we would have alreayd move the cgroup
> information to the new page. We have
> 
> 	h_cg = hugetlb_cgroup_from_page(oldhpage);
> 	set_hugetlb_cgroup(oldhpage, NULL);
> 
> 	/* move the h_cg details to new cgroup */
> 	set_hugetlb_cgroup(newhpage, h_cg);
> 
> 
> in hugetlb_cgroup_migrate

Yes but the res counter charge would be missing for the newpage after
put_page

-- 
Michal Hocko
SUSE Labs
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