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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>
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14
mm/filemap.c
14
mm/filemap.c
@ -3492,7 +3492,15 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
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if (PageHWPoison(page + count))
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goto skip;
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(*mmap_miss)++;
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/*
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* If there are too many folios that are recently evicted
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* in a file, they will probably continue to be evicted.
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* In such situation, read-ahead is only a waste of IO.
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* Don't decrease mmap_miss in this scenario to make sure
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* we can stop read-ahead.
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*/
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if (!folio_test_workingset(folio))
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(*mmap_miss)++;
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/*
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* NOTE: If there're PTE markers, we'll leave them to be
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@ -3541,7 +3549,9 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
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if (PageHWPoison(page))
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return ret;
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(*mmap_miss)++;
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/* See comment of filemap_map_folio_range() */
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if (!folio_test_workingset(folio))
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(*mmap_miss)++;
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/*
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* NOTE: If there're PTE markers, we'll leave them to be
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