Visualizing Linux IO with Seekwatcher and blktrace
Seekwatcher is a super cool utility for Linux that allows you to visualize the IO patterns on a running Linux box.
Check out the movies that are on the page.
This is all based on blktrace which is uses debugfs which is available on modern kernels.
I still need to get a vfsstat program like iostat and blktrace which shows files and offset and block length reads. From this I can then compute VFS page cache efficiency.