mm/khugepaged: sched to numa node when collapse huge page

Collapsing a huge page will copy huge page from general small pages, dest
node is calculated from most one of source pages, however THP daemon is
not scheduled on dest node.  The performance may be poor since huge page
copying across nodes, also cache is not used for target node.  With this
patch, khugepaged daemon switches to the same numa node with huge page.
It saves copying time and makes use of local cache better.

With this patch, specint 2006 base performance is improved with 6% on
Loongson 3C5000L platform with 32 cores and 8 numa nodes.

Link: https://lkml.kernel.org/r/20220317065024.2635069-1-maobibo@loongson.cn
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index edd643de2347553c09f3bdc7186193cf0cf46029..4688a6df035b5ded2371733cfa2f2803216e0b41 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1055,6 +1055,7 @@ static void collapse_huge_page(struct mm_struct *mm,
        struct vm_area_struct *vma;
        struct mmu_notifier_range range;
        gfp_t gfp;
+       const struct cpumask *cpumask;
 
        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
@@ -1068,6 +1069,13 @@ static void collapse_huge_page(struct mm_struct *mm,
         * that. We will recheck the vma after taking it again in write mode.
         */
        mmap_read_unlock(mm);
+
+       /* sched to specified node before huage page memory copy */
+       if (task_node(current) != node) {
+               cpumask = cpumask_of_node(node);
+               if (!cpumask_empty(cpumask))
+                       set_cpus_allowed_ptr(current, cpumask);
+       }
        new_page = khugepaged_alloc_page(hpage, gfp, node);
        if (!new_page) {
                result = SCAN_ALLOC_HUGE_PAGE_FAIL;