The patch titled
Subject: mm/vmscan: drop checking if _deferred_list is empty before using TTU_SYNC
has been added to the -mm mm-unstable branch. Its filename is
mm-vmscan-drop-checking-if-_deferred_list-is-empty-before-using-ttu_sync.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-drop-checking-if-_deferred_list-is-empty-before-using-ttu_sync.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Barry Song <v-songbaohua@xxxxxxxx>
Subject: mm/vmscan: drop checking if _deferred_list is empty before using TTU_SYNC
Date: Sun, 30 Jun 2024 11:41:55 +1200
The optimization of list_empty(&folio->_deferred_list) aimed to prevent
increasing the PTL duration when a large folio is partially unmapped, for
example, from subpage 0 to subpage (nr - 2).
But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during
shrink_folio_list()") actually splits this kind of large folios. This
makes the "optimization" useless.
Additionally, the list_empty() technically required a data_race()
annotation.
Link: https://lkml.kernel.org/r/20240629234155.53524-1-21cnbao@xxxxxxxxx
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmscan.c~mm-vmscan-drop-checking-if-_deferred_list-is-empty-before-using-ttu_sync
+++ a/mm/vmscan.c
@@ -1291,7 +1291,7 @@ retry:
* try_to_unmap acquire PTL from the first PTE,
* eliminating the influence of temporary PTE values.
*/
- if (folio_test_large(folio) && list_empty(&folio->_deferred_list))
+ if (folio_test_large(folio))
flags |= TTU_SYNC;
try_to_unmap(folio, flags);
_
Patches currently in -mm which might be from v-songbaohua@xxxxxxxx are
tools-mm-introduce-a-tool-to-assess-swap-entry-allocation-for-thp_swapout.patch
mm-vmscan-drop-checking-if-_deferred_list-is-empty-before-using-ttu_sync.patch
