Re: [PATCH] Add nid sanity on alloc_pages_node

[gurudas pai <gurudas.pai@oracle.com>]

>>>>> On Fri, 13 Jul 2007 10:45:07 +0800 Joe Jin <joe.jin@oracle.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