linux-kernel - Re: [PATCH v2 12/20] mm, hugetlb: remove vma_has

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Message-ID: <87mwoa0yx5.fsf@linux.vnet.ibm.com>
Date:	Thu, 22 Aug 2013 16:34:22 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>
Subject: Re: [PATCH v2 12/20] mm, hugetlb: remove vma_has_reserves()

Joonsoo Kim <iamjoonsoo.kim@....com> writes:

> On Thu, Aug 22, 2013 at 02:14:38PM +0530, Aneesh Kumar K.V wrote:
>> Joonsoo Kim <iamjoonsoo.kim@....com> writes:
>> 
>> > vma_has_reserves() can be substituted by using return value of
>> > vma_needs_reservation(). If chg returned by vma_needs_reservation()
>> > is 0, it means that vma has reserves. Otherwise, it means that vma don't
>> > have reserves and need a hugepage outside of reserve pool. This definition
>> > is perfectly same as vma_has_reserves(), so remove vma_has_reserves().
>> >
>> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>> 
>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
>
> Thanks.
>
>> > @@ -580,8 +547,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
>> >  	 * have no page reserves. This check ensures that reservations are
>> >  	 * not "stolen". The child may still get SIGKILLed
>> >  	 */
>> > -	if (!vma_has_reserves(vma, chg) &&
>> > -			h->free_huge_pages - h->resv_huge_pages == 0)
>> > +	if (chg && h->free_huge_pages - h->resv_huge_pages == 0)
>> >  		return NULL;
>> >
>> >  	/* If reserves cannot be used, ensure enough pages are in the pool */
>> > @@ -600,7 +566,7 @@ retry_cpuset:
>> >  			if (page) {
>> >  				if (avoid_reserve)
>> >  					break;
>> > -				if (!vma_has_reserves(vma, chg))
>> > +				if (chg)
>> >  					break;
>> >
>> >  				SetPagePrivate(page);
>> 
>> Can you add a comment above both the place to explain why checking chg
>> is good enough ?
>
> Yes, I can. But it will be changed to use_reserve in patch 13 and it
> represent it's meaning perfectly. So commeting may be useless.

That should be ok, because having a comment in this patch helps in
understanding the patch better, even though you are removing that
later. 

-aneesh

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