linux-kernel - Re: [PATCH 1/9] mm, hugetlb: move up the code which check availability of free huge page

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Date:	Tue, 16 Jul 2013 10:16:07 +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
Subject: Re: [PATCH 1/9] mm, hugetlb: move up the code which check
 availability of free huge page

On Mon, Jul 15, 2013 at 07:31:33PM +0530, Aneesh Kumar K.V wrote:
> Joonsoo Kim <iamjoonsoo.kim@....com> writes:
> 
> > We don't need to proceede the processing if we don't have any usable
> > free huge page. So move this code up.
> 
> I guess you can also mention that since we are holding hugetlb_lock
> hstate values can't change.

Okay. I will mention this for v2.

> 
> 
> Also.
> 
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index e2bfbf7..d87f70b 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -539,10 +539,6 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> >  	struct zoneref *z;
> >  	unsigned int cpuset_mems_cookie;
> >
> > -retry_cpuset:
> > -	cpuset_mems_cookie = get_mems_allowed();
> > -	zonelist = huge_zonelist(vma, address,
> > -					htlb_alloc_mask, &mpol, &nodemask);
> >  	/*
> >  	 * A child process with MAP_PRIVATE mappings created by their parent
> >  	 * have no page reserves. This check ensures that reservations are
> > @@ -550,11 +546,16 @@ retry_cpuset:
> >  	 */
> >  	if (!vma_has_reserves(vma) &&
> >  			h->free_huge_pages - h->resv_huge_pages == 0)
> > -		goto err;
> > +		return NULL;
> >
> 
> If you don't do the above change, the patch will be much simpler. 

The patch will be, but output code will not.
With this change, we can remove one goto label('err:') and
this makes code more readable.

Thanks.

> 
> 
> >  	/* If reserves cannot be used, ensure enough pages are in the pool */
> >  	if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
> > -		goto err;
> > +		return NULL;
> > +
> 
> Same here. 
> 
> > +retry_cpuset:
> > +	cpuset_mems_cookie = get_mems_allowed();
> > +	zonelist = huge_zonelist(vma, address,
> > +					htlb_alloc_mask, &mpol, &nodemask);
> >
> >  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> >  						MAX_NR_ZONES - 1, nodemask) {
> > @@ -572,10 +573,6 @@ retry_cpuset:
> >  	if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page))
> >  		goto retry_cpuset;
> >  	return page;
> > -
> > -err:
> > -	mpol_cond_put(mpol);
> > -	return NULL;
> >  }
> >
> >  static void update_and_free_page(struct hstate *h, struct page *page)
> 
> -aneesh
> 
> --
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