[Freeswitch-users] high load with ~200 fax calls despite low CPU utilization and low IO wait

Steve Underwood steveu at coppice.org
Fri Aug 10 19:53:14 MSD 2012

On 08/10/2012 04:55 AM, Adam Johnston wrote:
> Hi all,
> My FreeSWITCH setup works as follow: I have a service that launches 
> and monitors faxes (via event sockets) on one of a few FreeSWITCH 
> instances. These FreeSWITCH instances are running on dual-core, 2ghz 
> CentOS 5.8 and CentOS 6.0 VMs. The issue is that once I get to ~200 
> simultaneous faxes on any one FreeSWITCH VM the load average shoots up 
> (typically ~30, although I've seen it get much higher) and the VM 
> becomes sluggish and occasionally unusable.
> top and sar output confirms that CPU utilization is pretty low, as are 
> IO wait and RAM usage.
> I'm using a git head from 2012-02-06, although I see the same problem 
> if update to a more current head. On the most recent head I tried 
> (2012-08-06) the issue is worse, and crashes with a backtrace similar 
> to this Jira, http://jira.freeswitch.org/browse/FS-2893 despite my 
> compiling Lua and including the FreeSWITCH bindings.
> These issues occur on both the CentOS 5.8 and 6.0 VMs. I'm in the 
> process of loading 5.8 onto a physical machine and testing there. It's 
> also worth nothing that this load issue does not occur when I launch 
> faxes from a script on one of the VMs.
> Has anyone else seen similar high load issues before?
> Many thanks,
> Adam Johnston
What are these 200 FAXes doing? sending or receiving? Using audio or 
T.38? It makes quite a different to the load. Sending 200 faxes by audio 
at 14,400bps will keep a dual core machine busy. I'm not sure you can 
trust the CPU utilisation figures in a VM environment.


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