From 1ebf26a9b338534def47f307c6c8694b6dfc0a79 Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Tue, 16 Jun 2009 15:31:19 -0700 Subject: [PATCH] readahead: make mmap_miss an unsigned int This makes the performance impact of possible mmap_miss wrap around to be temporary and tolerable: i.e. MMAP_LOTSAMISS=100 extra readarounds. Otherwise if ever mmap_miss wraps around to negative, it takes INT_MAX cache misses to bring it back to normal state. During the time mmap readaround will be _enabled_ for whatever wild random workload. That's almost permanent performance impact. Signed-off-by: Wu Fengguang Cc: Ying Han Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index ede84fa7da5..8146e0264ef 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -879,7 +879,7 @@ struct file_ra_state { there are only # of pages ahead */ unsigned int ra_pages; /* Maximum readahead window */ - int mmap_miss; /* Cache miss stat for mmap accesses */ + unsigned int mmap_miss; /* Cache miss stat for mmap accesses */ loff_t prev_pos; /* Cache last read() position */ }; -- 2.20.1