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

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Date:	Mon, 15 Jul 2013 19:31:33 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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, Joonsoo Kim <js1304@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 1/9] mm, hugetlb: move up the code which check availability of free huge page

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.


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. 


>  	/* 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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