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

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Date:	Tue, 9 Aug 2016 18:32:39 +0800
From:	zhong jiang <zhongjiang@...wei.com>
To:	Mike Kravetz <mike.kravetz@...cle.com>
CC:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	<akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: fix the incorrect hugepages count

On 2016/8/9 1:14, Mike Kravetz wrote:
> 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.
>
  we need to take free hugetlb pages into account.  of course, the allocated huge pages is no
  need to reduce.  The patch just reduce the free hugetlb pages count.

  Thanks
 zhongjiang