tree 17498d55af5b2a588e7e7111e927a099236ca770
parent 275b12bf5486f6f531111fd3d7dbbf01df427cfe
author Andi Kleen <ak@linux.intel.com> 1306282349 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1306337966 -0700

readahead: reduce unnecessary mmap_miss increases

The original INT_MAX is too large, reduce it to

- avoid unnecessarily dirtying/bouncing the cache line

- restore mmap read-around faster on changed access pattern

Background: in the mosbench exim benchmark which does multi-threaded page
faults on shared struct file, the ra->mmap_miss updates are found to cause
excessive cache line bouncing on tmpfs.  The ra state updates are needless
for tmpfs because it actually disabled readahead totally
(shmem_backing_dev_info.ra_pages == 0).

Tested-by: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>