Well, preventing read cache usage is pretty simple. You can do some raw-read tests with dd. You can also do some tests (one-time read only, unfortunately, using drop_caches):
Code:
drop_caches
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Writing to this will cause the kernel to drop clean caches, dentries and
inodes from memory, causing that memory to become free.
As this is a non-destructive operation and dirty objects are not freeable, the
user should run `sync' first.(see linux/Documentation/filesystems/proc.txt).
转自：http://blog.csdn.net/dux003/archive/2010/11/11/6003328.aspx
http://www.linuxquestions.org/questions/linux-kernel-70/how-to-disable-filesystem-cache-627012/