linux-kernel - Re: [PATCH -V4 08/10] hugetlbfs: Add a list for tracking in-use HugeTLB pages

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Message-ID: <20120329081157.GD30465@tiehlicka.suse.cz>
Date:	Thu, 29 Mar 2012 10:11:57 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, mgorman@...e.de,
	kamezawa.hiroyu@...fujitsu.com, dhillf@...il.com,
	aarcange@...hat.com, akpm@...ux-foundation.org, hannes@...xchg.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V4 08/10] hugetlbfs: Add a list for tracking in-use
 HugeTLB pages

On Wed 28-03-12 23:08:34, Aneesh Kumar K.V wrote:
> Michal Hocko <mhocko@...e.cz> writes:
> 
> > On Fri 16-03-12 23:09:28, Aneesh Kumar K.V wrote:
> >> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
> >> 
> >> hugepage_activelist will be used to track currently used HugeTLB pages.
> >> We need to find the in-use HugeTLB pages to support memcg removal.
> >> On memcg removal we update the page's memory cgroup to point to
> >> parent cgroup.
> >> 
> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> >> ---
> >>  include/linux/hugetlb.h |    1 +
> >>  mm/hugetlb.c            |   23 ++++++++++++++++++-----
> >>  2 files changed, 19 insertions(+), 5 deletions(-)
> >> 
> >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> >> index cbd8dc5..6919100 100644
> >> --- a/include/linux/hugetlb.h
> >> +++ b/include/linux/hugetlb.h
> > [...]
> >> @@ -2319,14 +2322,24 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
> >>  		page = pte_page(pte);
> >>  		if (pte_dirty(pte))
> >>  			set_page_dirty(page);
> >> -		list_add(&page->lru, &page_list);
> >> +
> >> +		spin_lock(&hugetlb_lock);
> >> +		list_move(&page->lru, &page_list);
> >> +		spin_unlock(&hugetlb_lock);
> >
> > Why do we really need the spinlock here?
> 
> 
> It does a list_del from hugepage_activelist.

right you are.
sorry

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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