Re: using pgmeter for benchmarking

[Avishay Traeger <atraeger@cs.sunysb.edu>]

On Thu, 2007-11-01 at 16:15 +0530, addy soft wrote:
> hello all,
> 
> I am a newbie in filesystem field and wanted to benchmark filesystem
> using pgmeter.
> 
> But the source that i have downloaded from
> http://pgmeter.sourceforge.net/  CVS seems to be too old and have a
> kernel patch with it which is for kernel 2.2.6.
> 
> There is a syscall implemented with that version of pgmeter which is
> used to flush the page cache for a particular file.

Since 2.6.16 there has been a drop_caches proc file.  Instead of porting
this system call, I think you could modify pgmeter to use this.  Here
are some details:

===============================================
Writing to this will cause the kernel to drop clean caches, dentries and
inodes from memory, causing that memory to become free.
To free pagecache:
      * echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes:
      * echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries and inodes:
      * echo 3 > /proc/sys/vm/drop_caches
As this is a non-destructive operation and dirty objects are not
freeable, the user should run "sync" first!
===============================================

So instead of calling the system call, you should be able to call sync()
and then write either 1 or 3 to the proc file.

Hope that helps!
Avishay