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

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Message-ID: <20130823061653.GC22605@lge.com>
Date:	Fri, 23 Aug 2013 15:16:53 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.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()

On Thu, Aug 22, 2013 at 04:34:22PM +0530, Aneesh Kumar K.V wrote:
> 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. 

Okay. I will add it in next spin.

Thanks.
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