From 5c46d5319bde73075c5f2cefd555426848eb506f Mon Sep 17 00:00:00 2001 From: Liu Shixin Date: Fri, 22 Mar 2024 17:35:55 +0800 Subject: [PATCH] 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 Reviewed-by: Jan Kara Cc: Al Viro Cc: Christian Brauner Cc: Jinjiang Tu Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/filemap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 60890758d660..480ae6589803 100644 --- 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