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migrate_pages(): fix THP failure counting for -ENOMEM 

In unmap_and_move(), if the new THP cannot be allocated, -ENOMEM will be
returned, and migrate_pages() will try to split the THP unless "reason" is
MR_NUMA_MISPLACED (that is, nosplit == true).  But when nosplit == true,
the THP migration failure will not be counted.

This is incorrect, so in this patch, the THP migration failure will be
counted for -ENOMEM regardless of nosplit is true or false.  The nr_failed
counting isn't fixed because it's not used.  Added some comments for it
per Baolin's suggestion.

Link: https://lkml.kernel.org/r/20220817081408.513338-4-ying.huang@intel.com
Fixes: 5984fabb6e ("mm: move_pages: report the number of non-attempted pages")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Huang Ying 2022-08-17 16:14:03 +08:00 committed by Andrew Morton
parent 9c62ff005f
commit fbed53b477
1 changed files with 4 additions and 3 deletions
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7
mm/migrate.c
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@ -1494,11 +1494,11 @@ retry:
/*
* When memory is low, don't bother to try to migrate
* other pages, just exit.
* THP NUMA faulting doesn't split THP to retry.
*/
if (is_thp && !nosplit) {
if (is_thp) {
nr_thp_failed++;
if (!try_split_thp(page, &thp_split_pages)) {
/* THP NUMA faulting doesn't split THP to retry. */
if (!nosplit && !try_split_thp(page, &thp_split_pages)) {
nr_thp_split++;
goto retry;
}
@ -1514,6 +1514,7 @@ retry:
* the caller otherwise the page refcnt will be leaked.
*/
list_splice_init(&thp_split_pages, from);
/* nr_failed isn't updated for not used */
nr_thp_failed += thp_retry;
goto out;
case -EAGAIN: