(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.
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@xxxxxxxxx>
> Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
> ---
> 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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