High CPU usage on posix_fallocate call - CVS version

Corinna Vinschen corinna-cygwin@cygwin.com
Mon Nov 5 11:23:00 GMT 2007


On Nov  2 17:42, Rob Bosch wrote:
> I found on MSDN that Windows has the capfilealloc function in all Windows OS
> versions.  This function was designed to create a preallocated capture file
> of a specified size.  It seems like this would accomplish what cygwin needs
> with the posix_fallocate function?

Not at all.  Did you *read* what this method is about?

> -----Original Message-----
> From: Rob Bosch [mailto:XXXXXXXX@XXX.XXX] 

Even though this is your own mail address, please:

  http://cygwin.com/acronyms/#PCYMTNQREAIYR

  http://cygwin.com/acronyms/#TOFU

> When my compiled version of rsync is using the posix_fallocate function IÂ’m
> getting significant CPU usage. [...]
> getting 20%-25% CPU utilization during the posix_fallocate call. [...]
> It also takes 20 minutes for the file to be created using this call.

I can't reproduce this behaviour.  I created a 40 Gigs file (haven't 77
Gigs left) on my XP box using the posix_fallocate function (which, btw.,
is basically just a single native NT call under the hood) and it takes
roughly a few milliseconds.

Did you look for http://cygwin.com/acronyms/#BLODA ?

http://cygwin.com/ml/cygwin-talk/2007-q4/msg00026.html


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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