Commit 5c46d531 authored Mar 22, 2024 by Liu Shixin Committed by Andrew Morton Apr 25, 2024

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>

parent 0fd44ab2

mm/filemap.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -3492,6 +3492,14 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
		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)++;

		/*
		@@ -3541,6 +3549,8 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
		if (PageHWPoison(page))
		return ret;

		/* See comment of filemap_map_folio_range() */
		if (!folio_test_workingset(folio))
		(*mmap_miss)++;

		/*