The patch titled
Subject: mm/filemap: don't decrease mmap_miss when folio has workingset flag
has been added to the -mm mm-unstable branch. Its filename is
mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags-fix.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: Liu Shixin <liushixin2@xxxxxxxxxx>
Subject: mm/filemap: don't decrease mmap_miss when folio has workingset flag
Date: Tue, 26 Mar 2024 14:50:26 +0800
add comments
Link: https://lkml.kernel.org/r/20240326065026.1910584-1-liushixin2@xxxxxxxxxx
Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/filemap.c~mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags-fix
+++ a/mm/filemap.c
@@ -3492,6 +3492,13 @@ static vm_fault_t filemap_map_folio_rang
if (PageHWPoison(page + count))
goto skip;
+ /*
+ * If there are too many folios that are recently evicted
+ * in a file, they will probably continue to be evicted.
+ * In such situation, read-ahead is only a waste of IO.
+ * Don't decrease mmap_miss in this scenario to make sure
+ * we can stop read-ahead.
+ */
if (!folio_test_workingset(folio))
(*mmap_miss)++;
@@ -3542,6 +3549,7 @@ static vm_fault_t filemap_map_order0_fol
if (PageHWPoison(page))
return ret;
+ /* See comment of filemap_map_folio_range() */
if (!folio_test_workingset(folio))
(*mmap_miss)++;
_
Patches currently in -mm which might be from liushixin2@xxxxxxxxxx are
mm-readahead-break-read-ahead-loop-if-filemap_add_folio-return-enomem.patch
mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags.patch
mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags-fix.patch
