linux-kernel - Re: [PATCH] mm: fix the incorrect hugepages count

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Date:	Mon, 8 Aug 2016 10:14:48 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	zhongjiang <zhongjiang@...wei.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	akpm@...ux-foundation.org
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: fix the incorrect hugepages count

On 08/07/2016 07:49 PM, zhongjiang wrote:
> From: zhong jiang <zhongjiang@...wei.com>
> 
> when memory hotplug enable, free hugepages will be freed if movable node offline.
> therefore, /proc/sys/vm/nr_hugepages will be incorrect.
> 
> The patch fix it by reduce the max_huge_pages when the node offline.
> 
> Signed-off-by: zhong jiang <zhongjiang@...wei.com>
> ---
>  mm/hugetlb.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index f904246..3356e3a 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1448,6 +1448,7 @@ static void dissolve_free_huge_page(struct page *page)
>  		list_del(&page->lru);
>  		h->free_huge_pages--;
>  		h->free_huge_pages_node[nid]--;
> +		h->max_huge_pages--;
>  		update_and_free_page(h, page);
>  	}
>  	spin_unlock(&hugetlb_lock);
> 

Adding Naoya as he was the original author of this code.

>From quick look it appears that the huge page will be migrated (allocated
on another node).  If my understanding is correct, then max_huge_pages
should not be adjusted here.

-- 
Mike Kravetz