maillist inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8EXN6
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?...
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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 flags. The async path is not to care because in above scenario, it's hard to run into the async path.
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 Conflicts: mm/filemap.c Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/filemap.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c index 2eeb9978f39e..b48ec6fc8f4b 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3168,7 +3168,14 @@ void filemap_map_pages(struct vm_fault *vmf, if (xas.xa_index >= max_idx) goto unlock;
- if (mmap_miss > 0) + /* + * If there are too many pages 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 (mmap_miss > 0 && !PageWorkingset(page)) mmap_miss--;
vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT;