The patch titled
Subject: mm/migrate: __unmap_and_move() push good newpage to LRU
has been added to the -mm tree. Its filename is
mm-migrate-__unmap_and_move-push-good-newpage-to-lru.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-__unmap_and_move-push-good-newpage-to-lru.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-__unmap_and_move-push-good-newpage-to-lru.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/migrate: __unmap_and_move() push good newpage to LRU
Compaction, NUMA page movement, THP collapse/split, and memory failure do
isolate unevictable pages from their "LRU", losing the record of
mlock_count in doing so (isolators are likely to use page->lru for their
own private lists, so mlock_count has to be presumed lost).
That's unfortunate, and we should put in some work to correct that: one
can imagine a function to build up the mlock_count again - but it would
require i_mmap_rwsem for read, so be careful where it's called. Or
page_referenced_one() and try_to_unmap_one() might do that extra work.
But one place that can very easily be improved is page migration's
__unmap_and_move(): a small adjustment to where the successful new page is
put back on LRU, and its mlock_count (if any) is built back up by
remove_migration_ptes().
Link: https://lkml.kernel.org/r/269eec24-978a-984a-8a85-1d29f36ad343@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)
--- a/mm/migrate.c~mm-migrate-__unmap_and_move-push-good-newpage-to-lru
+++ a/mm/migrate.c
@@ -1034,6 +1034,21 @@ static int __unmap_and_move(struct page
if (!page_mapped(page))
rc = move_to_new_page(newpage, page, mode);
+ /*
+ * When successful, push newpage to LRU immediately: so that if it
+ * turns out to be an mlocked page, remove_migration_ptes() will
+ * automatically build up the correct newpage->mlock_count for it.
+ *
+ * We would like to do something similar for the old page, when
+ * unsuccessful, and other cases when a page has been temporarily
+ * isolated from the unevictable LRU: but this case is the easiest.
+ */
+ if (rc == MIGRATEPAGE_SUCCESS) {
+ lru_cache_add(newpage);
+ if (page_was_mapped)
+ lru_add_drain();
+ }
+
if (page_was_mapped)
remove_migration_ptes(page,
rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
@@ -1047,20 +1062,12 @@ out_unlock:
unlock_page(page);
out:
/*
- * If migration is successful, decrease refcount of the newpage
+ * If migration is successful, decrease refcount of the newpage,
* which will not free the page because new page owner increased
- * refcounter. As well, if it is LRU page, add the page to LRU
- * list in here. Use the old state of the isolated source page to
- * determine if we migrated a LRU page. newpage was already unlocked
- * and possibly modified by its owner - don't rely on the page
- * state.
+ * refcounter.
*/
- if (rc == MIGRATEPAGE_SUCCESS) {
- if (unlikely(!is_lru))
- put_page(newpage);
- else
- putback_lru_page(newpage);
- }
+ if (rc == MIGRATEPAGE_SUCCESS)
+ put_page(newpage);
return rc;
}
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-munlock-delete-page_mlock-and-all-its-works.patch
mm-munlock-delete-foll_mlock-and-foll_populate.patch
mm-munlock-delete-munlock_vma_pages_all-allow-oomreap.patch
mm-munlock-rmap-call-mlock_vma_page-munlock_vma_page.patch
mm-munlock-replace-clear_page_mlock-by-final-clearance.patch
mm-munlock-maintain-page-mlock_count-while-unevictable.patch
mm-munlock-mlock_pte_range-when-mlocking-or-munlocking.patch
mm-migrate-__unmap_and_move-push-good-newpage-to-lru.patch
mm-munlock-delete-smp_mb-from-__pagevec_lru_add_fn.patch
mm-munlock-mlock_page-munlock_page-batch-by-pagevec.patch
mm-munlock-page-migration-needs-mlock-pagevec-drained.patch
mm-thp-collapse_file-do-try_to_unmapttu_batch_flush.patch
mm-thp-shrink_page_list-avoid-splitting-vm_locked-thp.patch
