Re: [PATCH 2/2] mm: thp: khugepaged: add policy for finding target node

[Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>]

(2013/09/10 9:55), Wanpeng Li wrote:
> On Tue, Sep 10, 2013 at 09:45:09AM +0900, Yasuaki Ishimatsu wrote:
>> (2013/09/02 12:45), Bob Liu wrote:
>>> Currently khugepaged will try to merge HPAGE_PMD_NR normal pages to a huge page
>>> which is allocated from the node of the first normal page, this policy is very
>>> rough and may affect userland applications.
>>
>>> Andrew Davidoff reported a related issue several days ago.
>>
>> Where is an original e-mail?
>> I tried to find original e-mail in my mailbox. But I cannot find it.
>>
>

> http://marc.info/?l=linux-mm&m=137701470529356&w=2

Thank you for informing it.

Thanks,
Yasuaki Ishimatsu

>
>> Thanks,
>> Yasuaki Ishimatsu
>>
>>>
>>> Using "numactl --interleave=all ./test" to run the testcase, but the result
>>> wasn't not as expected.
>>> cat /proc/2814/numa_maps:
>>> 7f50bd440000 interleave:0-3 anon=51403 dirty=51403 N0=435 N1=435 N2=435
>>> N3=50098
>>> The end results showed that most pages are from Node3 instead of interleave
>>> among node0-3 which was unreasonable.
>>>
>>> This patch adds a more complicated policy.
>>> When searching HPAGE_PMD_NR normal pages, record which node those pages come
>>> from. Alway allocate hugepage from the node with the max record. If several
>>> nodes have the same max record, try to interleave among them.
>>>
>>> After this patch the result was as expected:
>>> 7f78399c0000 interleave:0-3 anon=51403 dirty=51403 N0=12723 N1=12723 N2=13235
>>> N3=12722
>>>
>>> The simple testcase is like this:
>>> #include<stdio.h>
>>> #include<stdlib.h>
>>>
>>> int main() {
>>> 	char *p;
>>> 	int i;
>>> 	int j;
>>>
>>> 	for (i=0; i < 200; i++) {
>>> 		p = (char *)malloc(1048576);
>>> 		printf("malloc done\n");
>>>
>>> 		if (p == 0) {
>>> 			printf("Out of memory\n");
>>> 			return 1;
>>> 		}
>>> 		for (j=0; j < 1048576; j++) {
>>> 			p[j] = 'A';
>>> 		}
>>> 		printf("touched memory\n");
>>>
>>> 		sleep(1);
>>> 	}
>>> 	printf("enter sleep\n");
>>> 	while(1) {
>>> 		sleep(100);
>>> 	}
>>> }
>>>
>>> Reported-by: Andrew Davidoff <davidoff@qedmf.net>
>>> Signed-off-by: Bob Liu <bob.liu@oracle.com>
>>> ---
>>>    mm/huge_memory.c |   50 +++++++++++++++++++++++++++++++++++++++++---------
>>>    1 file changed, 41 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index 7448cf9..86c7f0d 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -2144,7 +2144,33 @@ static void khugepaged_alloc_sleep(void)
>>>    			msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
>>>    }
>>>
>>> +static int khugepaged_node_load[MAX_NUMNODES];
>>>    #ifdef CONFIG_NUMA
>>> +static int last_khugepaged_target_node = NUMA_NO_NODE;
>>> +static int khugepaged_find_target_node(void)
>>> +{
>>> +	int i, target_node = 0, max_value = 1;
>>> +
>>> +	/* find first node with most normal pages hit */
>>> +	for (i = 0; i < MAX_NUMNODES; i++)
>>> +		if (khugepaged_node_load[i] > max_value) {
>>> +			max_value = khugepaged_node_load[i];
>>> +			target_node = i;
>>> +		}
>>> +
>>> +	/* do some balance if several nodes have the same hit number */
>>> +	if (target_node <= last_khugepaged_target_node) {
>>> +		for (i = last_khugepaged_target_node + 1; i < MAX_NUMNODES; i++)
>>> +			if (max_value == khugepaged_node_load[i]) {
>>> +				target_node = i;
>>> +				break;
>>> +			}
>>> +	}
>>> +
>>> +	last_khugepaged_target_node = target_node;
>>> +	return target_node;
>>> +}
>>> +
>>>    static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
>>>    {
>>>    	if (IS_ERR(*hpage)) {
>>> @@ -2178,9 +2204,8 @@ static struct page
>>>    	 * mmap_sem in read mode is good idea also to allow greater
>>>    	 * scalability.
>>>    	 */
>>> -	*hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
>>> -				      node, __GFP_OTHER_NODE);
>>> -
>>> +	*hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask(
>>> +			khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER);
>>>    	/*
>>>    	 * After allocating the hugepage, release the mmap_sem read lock in
>>>    	 * preparation for taking it in write mode.
>>> @@ -2196,6 +2221,11 @@ static struct page
>>>    	return *hpage;
>>>    }
>>>    #else
>>> +static int khugepaged_find_target_node(void)
>>> +{
>>> +	return 0;
>>> +}
>>> +
>>>    static inline struct page *alloc_hugepage(int defrag)
>>>    {
>>>    	return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
>>> @@ -2405,6 +2435,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
>>>    	if (pmd_trans_huge(*pmd))
>>>    		goto out;
>>>
>>> +	memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
>>>    	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
>>>    	for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
>>>    	     _pte++, _address += PAGE_SIZE) {
>>> @@ -2421,12 +2452,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
>>>    		if (unlikely(!page))
>>>    			goto out_unmap;
>>>    		/*
>>> -		 * Chose the node of the first page. This could
>>> -		 * be more sophisticated and look at more pages,
>>> -		 * but isn't for now.
>>> +		 * Chose the node of most normal pages hit, record this
>>> +		 * informaction to khugepaged_node_load[]
>>>    		 */
>>> -		if (node == NUMA_NO_NODE)
>>> -			node = page_to_nid(page);
>>> +		node = page_to_nid(page);
>>> +		khugepaged_node_load[node]++;
>>>    		VM_BUG_ON(PageCompound(page));
>>>    		if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
>>>    			goto out_unmap;
>>> @@ -2441,9 +2471,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
>>>    		ret = 1;
>>>    out_unmap:
>>>    	pte_unmap_unlock(pte, ptl);
>>> -	if (ret)
>>> +	if (ret) {
>>> +		node = khugepaged_find_target_node();
>>>    		/* collapse_huge_page will return with the mmap_sem released */
>>>    		collapse_huge_page(mm, address, hpage, vma, node);
>>> +	}
>>>    out:
>>>    	return ret;
>>>    }
>>>
>>
>>
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