| Message ID | 20210413212416.3273-8-shy828301@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: thp: use generic THP migration for NUMA hinting fault | expand |
On Tue, Apr 13, 2021 at 02:24:16PM -0700, Yang Shi wrote: > A quick grep shows x86_64, PowerPC (book3s), ARM64 and S390 support both > NUMA balancing and THP. But S390 doesn't support THP migration so NUMA > balancing actually can't migrate any misplaced pages. > > Skip make PMD PROT_NONE for such case otherwise CPU cycles may be wasted > by pointless NUMA hinting faults on S390. > > Signed-off-by: Yang Shi <shy828301@gmail.com> Acked-by: Mel Gorman <mgorman@suse.de>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 94981907fd4c..f63445f3a17d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1741,6 +1741,7 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, * Returns * - 0 if PMD could not be locked * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary + * or if prot_numa but THP migration is not supported * - HPAGE_PMD_NR if protections changed and TLB flush necessary */ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, @@ -1755,6 +1756,9 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; + if (prot_numa && !thp_migration_supported()) + return 1; + ptl = __pmd_trans_huge_lock(pmd, vma); if (!ptl) return 0;
A quick grep shows x86_64, PowerPC (book3s), ARM64 and S390 support both NUMA balancing and THP. But S390 doesn't support THP migration so NUMA balancing actually can't migrate any misplaced pages. Skip make PMD PROT_NONE for such case otherwise CPU cycles may be wasted by pointless NUMA hinting faults on S390. Signed-off-by: Yang Shi <shy828301@gmail.com> --- mm/huge_memory.c | 4 ++++ 1 file changed, 4 insertions(+)