How to flush the disk read cache under Windows?

Question

In order to be able to so some benchmarks I need to cleanup Windows disk read cache. How can I do this?

In fact I want to compare if loading a big Unicode file (UTF-8 or UTF-16) from disk is faster or not, considering that in memory I do keep UTF-16.

I know that it should be no significant difference but in order to benchmark it I need to be sure that that file is not cached - I need to see if size on disk has more or less impact than decoding the file.

Answer 1

Asked and answered, my friend:

http://stackoverflow.com/questions/85595/flush-disk-cache-from-windows-cli

Otherwise, try here:

http://www.google.com/search?q=flush+the+disk+read+cache+Windows%3F&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

Answer 2

The only solution I found so far was http://chadaustin.me/2009/04/flushing-disk-cache/ but this ones takes too much time so I hope we'll find a better one.

Answer 3

AFAIK, it's unfortunately not possible to discard the read cache under Windows. I spent some time looking into this some years ago, and only found out how to flush the write cache.

As I see it, you have three options, unless somebody else has found some magic:

1. If possible, do your read file I/O in unbuffered mode.
2. Each time you want to benchmark, create a new copy of the test data specifying unbuffered mode when creating the new copy (this should keep the copy out of read cache, but I haven't tested).
3. Allocate enough memory that windows has to discard the disk cache (ugh!).