linux-kernel - Re: [PATCH] Add nid sanity on alloc_pages

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Message-ID: <469771F2.6000901@oracle.com>
Date:	Fri, 13 Jul 2007 18:07:06 +0530
From:	gurudas pai <gurudas.pai@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Joe Jin <joe.jin@...cle.com>, bill.irwin@...cle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add nid sanity on alloc_pages_node


>>>>> On Fri, 13 Jul 2007 10:45:07 +0800 Joe Jin <joe.jin@...cle.com> wrote:
>>>>>
>>>>> Something like this?
>>>>>
>>>>> --- a/mm/hugetlb.c~a
>>>>> +++ a/mm/hugetlb.c
>>>>> @@ -105,13 +105,20 @@ static void free_huge_page(struct page *
>>>>>  
>>>>>  static int alloc_fresh_huge_page(void)
>>>>>  {
>>>>> -	static int nid = 0;
>>>>> +	static int prev_nid;
>>>>> +	static DEFINE_SPINLOCK(nid_lock);
>>>>>  	struct page *page;
>>>>> -	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
>>>>> -					HUGETLB_PAGE_ORDER);
>>>>> -	nid = next_node(nid, node_online_map);
>>>>> +	int nid;
>>>>> +
>>>>> +	spin_lock(&nid_lock);
>>>>> +	nid = next_node(prev_nid, node_online_map);
>>>>>  	if (nid == MAX_NUMNODES)
>>>>>  		nid = first_node(node_online_map);
>>>>> +	prev_nid = nid;
>>>>> +	spin_unlock(&nid_lock);
>>>>> +
>>>>> +	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
>>>>> +					HUGETLB_PAGE_ORDER);
>>>>>  	if (page) {
>>>>>  		set_compound_page_dtor(page, free_huge_page);
>>>>>  		spin_lock(&hugetlb_lock);
>>>>> _
>>>>>
>> I think this will never get pages from node 0 ? Because nid = 
>> next_node(prev_node,node_online_map) and even if prev_node = 0, nid will 
>> become 1.
>
> It'll start out at node 1.  But it will visit the final node (which is less
> than MAX_NUMNODES) and will then advance onto the fist node (which can be
>> = 0).
>
> This code needs a bit of thought and testing for the non-numa case too
> please.  At the least, there might be optimisation opportunities.
I tested on non-numa machine. Your patch works fine.

Thanks,
-Guru


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