mm: numa: Migrate pages handled during a pmd_numa hinting fault
To say that the PMD handling code was incorrectly transferred from autonuma
is an understatement. The intention was to handle a PMDs worth of pages
in the same fault and effectively batch the taking of the PTL and page
migration. The copied version instead has the impact of clearing a number
of pte_numa PTE entries and whether any page migration takes place depends
on racing. This just happens to work in some cases.
This patch handles pte_numa faults in batch when a pmd_numa fault is
handled. The pages are migrated if they are currently misplaced.
Essentially this is making an assumption that NUMA locality is
on a PMD boundary but that could be addressed by only setting
pmd_numa if all the pages within that PMD are on the same node
if necessary.
Signed-off-by: Mel Gorman <mgorman@suse.de>
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 7ef6ae9..dce6fb4 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -37,12 +37,14 @@
static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end, pgprot_t newprot,
- int dirty_accountable, int prot_numa)
+ int dirty_accountable, int prot_numa, bool *ret_all_same_node)
{
struct mm_struct *mm = vma->vm_mm;
pte_t *pte, oldpte;
spinlock_t *ptl;
unsigned long pages = 0;
+ bool all_same_node = true;
+ int last_nid = -1;
pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
arch_enter_lazy_mmu_mode();
@@ -61,6 +63,12 @@
page = vm_normal_page(vma, addr, oldpte);
if (page) {
+ int this_nid = page_to_nid(page);
+ if (last_nid == -1)
+ last_nid = this_nid;
+ if (last_nid != this_nid)
+ all_same_node = false;
+
/* only check non-shared pages */
if (!pte_numa(oldpte) &&
page_mapcount(page) == 1) {
@@ -81,7 +89,6 @@
if (updated)
pages++;
-
ptep_modify_prot_commit(mm, addr, pte, ptent);
} else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
swp_entry_t entry = pte_to_swp_entry(oldpte);
@@ -101,6 +108,7 @@
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(pte - 1, ptl);
+ *ret_all_same_node = all_same_node;
return pages;
}
@@ -127,6 +135,7 @@
pmd_t *pmd;
unsigned long next;
unsigned long pages = 0;
+ bool all_same_node;
pmd = pmd_offset(pud, addr);
do {
@@ -143,9 +152,15 @@
if (pmd_none_or_clear_bad(pmd))
continue;
pages += change_pte_range(vma, pmd, addr, next, newprot,
- dirty_accountable, prot_numa);
+ dirty_accountable, prot_numa, &all_same_node);
- if (prot_numa)
+ /*
+ * If we are changing protections for NUMA hinting faults then
+ * set pmd_numa if the examined pages were all on the same
+ * node. This allows a regular PMD to be handled as one fault
+ * and effectively batches the taking of the PTL
+ */
+ if (prot_numa && all_same_node)
change_pmd_protnuma(vma->vm_mm, addr, pmd);
} while (pmd++, addr = next, addr != end);