linux-kernel - Re: [PATCH v2 03/20] mm, hugetlb: fix subpool accounting handling

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Message-ID: <87vc2zgzpn.fsf@linux.vnet.ibm.com>
Date:	Wed, 21 Aug 2013 14:58:20 +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>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 03/20] mm, hugetlb: fix subpool accounting handling

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

> If we alloc hugepage with avoid_reserve, we don't dequeue reserved one.
> So, we should check subpool counter when avoid_reserve.
> This patch implement it.

Can you explain this better ? ie, if we don't have a reservation in the
area chg != 0. So why look at avoid_reserve. 

Also the code will become if you did

if (!chg && avoid_reserve)
   chg = 1;

and then rest of the code will be able to handle the case.

>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 12b6581..ea1ae0a 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1144,13 +1144,14 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
>  	chg = vma_needs_reservation(h, vma, addr);
>  	if (chg < 0)
>  		return ERR_PTR(-ENOMEM);
> -	if (chg)
> -		if (hugepage_subpool_get_pages(spool, chg))
> +	if (chg || avoid_reserve)
> +		if (hugepage_subpool_get_pages(spool, 1))
>  			return ERR_PTR(-ENOSPC);
>
>  	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
>  	if (ret) {
> -		hugepage_subpool_put_pages(spool, chg);
> +		if (chg || avoid_reserve)
> +			hugepage_subpool_put_pages(spool, 1);
>  		return ERR_PTR(-ENOSPC);
>  	}
>  	spin_lock(&hugetlb_lock);
> @@ -1162,7 +1163,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
>  			hugetlb_cgroup_uncharge_cgroup(idx,
>  						       pages_per_huge_page(h),
>  						       h_cg);
> -			hugepage_subpool_put_pages(spool, chg);
> +			if (chg || avoid_reserve)
> +				hugepage_subpool_put_pages(spool, 1);
>  			return ERR_PTR(-ENOSPC);
>  		}
>  		spin_lock(&hugetlb_lock);
> -- 
> 1.7.9.5

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