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mm: thp: skip make PMD PROT_NONE if THP migration is not supported

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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.

Link: https://lkml.kernel.org/r/20210518200801.7413-8-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Shi 2021-06-30 18:51:55 -07:00 committed by Linus Torvalds
parent 662aeea753
commit e346e6688c
1 changed files with 4 additions and 0 deletions
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4
mm/huge_memory.c
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@ -1742,6 +1742,7 @@ 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,
@ -1756,6 +1757,9 @@ 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;