linux-kernel - Re: [RFC PATCH 4/4] hugetlb: add support for preferred node to alloc_huge_page

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Message-ID: <20170612114800.GJ7476@dhcp22.suse.cz>
Date:   Mon, 12 Jun 2017 13:48:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Xishi Qiu <qiuxishi@...wei.com>,
        zhong jiang <zhongjiang@...wei.com>,
        Joonsoo Kim <js1304@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 4/4] hugetlb: add support for preferred node to
 alloc_huge_page_nodemask

On Mon 12-06-17 11:06:56, Michal Hocko wrote:
[...]
> @@ -1723,29 +1729,26 @@ struct page *alloc_huge_page_node(struct hstate *h, int nid)
>  	return page;
>  }
>  
> -struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask)
> +struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> +		nodemask_t *nmask)
>  {
>  	struct page *page = NULL;
> -	int node;
>  
>  	spin_lock(&hugetlb_lock);
>  	if (h->free_huge_pages - h->resv_huge_pages > 0) {
> -		for_each_node_mask(node, *nmask) {
> -			page = dequeue_huge_page_node_exact(h, node);
> -			if (page)
> -				break;
> -		}
> +		page = dequeue_huge_page_nodemask(h, preferred_nid, nmask);
> +		if (page)
> +			goto unlock;
>  	}
> +unlock:
>  	spin_unlock(&hugetlb_lock);
>  	if (page)
>  		return page;
>  
>  	/* No reservations, try to overcommit */
> -	for_each_node_mask(node, *nmask) {
> -		page = __alloc_buddy_huge_page_no_mpol(h, node);
> -		if (page)
> -			return page;
> -	}
> +	page = __alloc_buddy_huge_page_no_mpol(h, preferred_nid);
> +	if (page)
> +		return page;

I was too quick. The fallback allocation needs some more love. I am
working on this but it quickly gets quite hairy so let's see whether
this still can converge to something reasonable.
-- 
Michal Hocko
SUSE Labs