[Serusers] Server dimensioning

[Miklos Tirpak]

Hi,

I think in most of the cases it is worth increasing the number of child 
processes. A child process is blocked during the SIP msg processing, and 
if there is any problem the blocking can take a lot of time, for example 
the processes can be blocked because of a not responding DNS server. 
When this happens SER cannot handle new incoming messages if there is no 
more child process available. Btw, even if there is still a child 
process available, if the new msg requires a DNS query again then there 
is not too much difference. But if the new msg is routed without being 
blocked again then it will be successfully handled by SER while the 
other messages are waiting for the response of the DNS server. (I think 
it is also worth setting the timeout of the DNS query (and other 
external queries) to a low value.)
And it is always good to increase the the number of processes when the 
limit is not the CPU but SER waits for some external source too much, 
for example lots of database queries to another server. -- SER can start 
processing the new messages at least while the previous ones are still 
waiting for the database result.

The memory usage is not increased too much by the number of processes 
because of the copy-on-write strategy of the OS. The number of file 
descriptors needed is increased, and each child process keeps a separate 
DB connection to the server. So you may have to increase the limits. 
Also keep in mind that when the number of processes is too high and they 
simultaneously try to access some shared resource that involves locking 
then the risk of contention is also high.

So in general, it is better to test it by yourself because the 
performance heavily depends on your configuration and the servers SER 
tries to access during the msg routing. Include the failure cases in 
your tests to find the optimum number of processes.

Regards,
Miklos

On 06/24/2009 02:45 PM, inge wrote:
> Hi all,
> 
> I wonder about the "child" parameter in ser.cfg.
> 
> What's the average processing capacity (number of requets/process) ?
> 
> Currently, the parameter is set to 4, the default value. What's the risk
> of the increase ?
> 
> SER runs on RedHat AS4 with Intel Xeon Quad 3.0 Ghz.
> 
> Thanks for your support.
> 
> _______________________________________________
> Serusers mailing list
> Serusers at lists.iptel.org
> http://lists.iptel.org/mailman/listinfo/serusers