linux-kernel - Re: [PATCH] mm/hugetlb_cgroup: Add list_del to remove unused page from hugepage

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Date:	Wed, 11 Jul 2012 17:17:14 +0800
From:	Wanpeng Li <liwp.linux@...il.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Li Zefan <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wanpeng Li <liwp.linux@...il.com>
Subject: Re: [PATCH] mm/hugetlb_cgroup: Add list_del to remove unused page
 from hugepage_activelist when hugepage migration

On Wed, Jul 11, 2012 at 02:02:23PM +0530, Aneesh Kumar K.V wrote:
>Wanpeng Li <liwp.linux@...il.com> writes:
>
>> From: Wanpeng Li <liwp@...ux.vnet.ibm.com>
>>
>> hugepage_activelist is used to track currently used HugeTLB pages.
>> We can find the in-use HugeTLB pages to support HugeTLB cgroup
>> removal. Don't keep unused page in hugetlb_activelist too long.
>> Otherwise, on cgroup removal we should update the unused page's 
>> charge to parent count. To reduce this overhead, remove unused page 
>> from hugepage_activelist immediately.
>>
>> Signed-off-by: Wanpeng Li <liwp.linux@...il.com>
>> ---
>>  mm/hugetlb_cgroup.c |    1 +
>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
>> index b834e8d..d819d66 100644
>> --- a/mm/hugetlb_cgroup.c
>> +++ b/mm/hugetlb_cgroup.c
>> @@ -398,6 +398,7 @@ void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
>>  	spin_lock(&hugetlb_lock);
>>  	h_cg = hugetlb_cgroup_from_page(oldhpage);
>>  	set_hugetlb_cgroup(oldhpage, NULL);
>> +	list_del(&oldhpage->lru);
>>
>>  	/* move the h_cg details to new cgroup */
>>  	set_hugetlb_cgroup(newhpage, h_cg);
>
>put_page on the oldhpage will do that. If we do list_del here
>free_huge_page() will have error list_move().

I don't know if move the page to other lists when migration in order 
to reduce overhead I mentioned make sense. :-)

Regards,
Wanpeng Li

>
>-aneesh
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