mm/filemap: don't decrease mmap_miss when folio has workingset flag

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>

diff --git a/mm/filemap.c b/mm/filemap.c
index 60890758d6605a75bffa658f30b947c1b1de6c82..480ae658980316ffb13bfc167d7826515268fcdc 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3492,7 +3492,15 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
                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_folio(struct vm_fault *vmf,
        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