mm: migrate: do not retry 10 times for the subpages of fail-to-migrate THP

If THP is failed to migrate due to -ENOSYS or -ENOMEM case, the THP will
be split, and the subpages of fail-to-migrate THP will be tried to migrate
again, so we should not account the retry counter in the second loop,
since we already accounted 'nr_thp_failed' in the first loop.

Moreover we also do not need retry 10 times for -EAGAIN case for the
subpages of fail-to-migrate THP in the second loop, since we already
regarded the THP as migration failure, and save some migration time (for
the worst case, will try 512 * 10 times) according to previous discussion
[1].

[1] https://lore.kernel.org/linux-mm/87r13a7n04.fsf@yhuang6-desk2.ccr.corp.intel.com/

Link: https://lkml.kernel.org/r/20220817081408.513338-9-ying.huang@intel.com
Tested-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: 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>

diff --git a/mm/migrate.c b/mm/migrate.c
index 55fbf96694313ff6758c00053d715195ceb977b4..06a6539778351bd92c030af01fa50ff290e44547 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1522,7 +1522,7 @@ thp_subpage_migration:
                        case -EAGAIN:
                                if (is_thp)
                                        thp_retry++;
-                               else
+                               else if (!no_subpage_counting)
                                        retry++;
                                nr_retry_pages += nr_subpages;
                                break;
@@ -1548,8 +1548,7 @@ thp_subpage_migration:
                        }
                }
        }
-       if (!no_subpage_counting)
-               nr_failed += retry;
+       nr_failed += retry;
        nr_thp_failed += thp_retry;
        nr_failed_pages += nr_retry_pages;
        /*