[merged mm-stable] mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags.patch removed from -mm tree

[merged mm-stable] mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/filemap: don't decrease mmap_miss when folio has workingset flag
has been removed from the -mm tree.  Its filename was
     mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Liu Shixin <liushixin2@huawei.com>
Subject: mm/filemap: don't decrease mmap_miss when folio has workingset flag
Date: Fri, 22 Mar 2024 17:35:55 +0800

If there are too many folios that are recently evicted in a file, then
they will probably continue to be evicted.  In such situation, there is no
positive effect to read-ahead this file since it is only a waste of IO.

The mmap_miss is increased in do_sync_mmap_readahead() and decreased in
both do_async_mmap_readahead() and filemap_map_pages().  In order to skip
read-ahead in above scenario, the mmap_miss have to increased exceed
MMAP_LOTSAMISS.  This can be done by stop decreased mmap_miss when folio
has workingset flag.  The async path is not to care because in above
scenario, it's hard to run into the async path.

[liushixin2@huawei.com: add comments]
  Link: https://lkml.kernel.org/r/20240326065026.1910584-1-liushixin2@huawei.com
Link: https://lkml.kernel.org/r/20240322093555.226789-3-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jinjiang Tu <tujinjiang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/filemap.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/mm/filemap.c~mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags
+++ a/mm/filemap.c
@@ -3492,7 +3492,15 @@ static vm_fault_t filemap_map_folio_rang
 		if (PageHWPoison(page + count))
 			goto skip;
 
-		(*mmap_miss)++;
+		/*
+		 * 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)++;
 
 		/*
 		 * NOTE: If there're PTE markers, we'll leave them to be
@@ -3541,7 +3549,9 @@ static vm_fault_t filemap_map_order0_fol
 	if (PageHWPoison(page))
 		return ret;
 
-	(*mmap_miss)++;
+	/* See comment of filemap_map_folio_range() */
+	if (!folio_test_workingset(folio))
+		(*mmap_miss)++;
 
 	/*
 	 * NOTE: If there're PTE markers, we'll leave them to be
_

Patches currently in -mm which might be from liushixin2@huawei.com are