Clear file cache to repeat performance testing

spdenne_11721 0
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What tools or techniques can I use to remove cached file contents to prevent my performance results from being skewed? I believe I need to either completely clear, or selectively remove cached information about file and directory contents.

The application that I'm developing is a specialised compression utility, and is expected to do a lot of work reading and writing files that the operating system hasn't touched recently, and whose disk blocks are unlikely to be cached.

I wish to remove the variability I see in IO time when I repeat the task of profiling different strategies for doing the file processing work.

I'm primarily interested in solutions for Windows XP, as that is my main development machine, but I can also test using linux, and so am interested in answers for that environment too.

I tried SysInternals CacheSet, but clicking "Clear" doesn't result in a measurable increase (restoration to timing after a cold-boot) in the time to re-read files I've just read a few times.

disk caching file performance
9 Answers

Use SysInternal's RAMMap app.

rammap empty standby

The Empty / Empty Standby List menu option will clear the Windows file cache.

user_12614310

A quick googling gives these options for Linux

  1. Unmount and mount the partition holding the files
  2. sync && echo 1 > /proc/sys/vm/drop_caches
John_Nilsson_242430

I've found one technique (other than rebooting) that seems to work:

  1. Run a few copies of MemAlloc
  2. With each one, allocate large chunks of memory a few times
  3. Use Process Explorer to observe the System Cache size reducing to very low levels
  4. Quit the MemAlloc programs

It isn't selective though. Ideally I'd like to be able to clear the specific portions of memory being used for caching the disk blocks of files that I want to no longer be cached.

spdenne_117210
user_70377960
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