disabling the caches in Linux
Sometimes you'd like to disable the file (and other caches) in Linux for performance testing reasons. Well, now you can. Simply:
To drop pagecache only, enter: echo 1 > /proc/sys/vm/drop_caches
2 is dentries and inodes only, and 3 is pagecache, dentries, and inodes. You can easily whip together a little script to drop caches regularly enough to simulate running with no caches.
(This information is also under "drop_caches" in linux/Documentation/filesystems/proc.txt.)