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CPU Limit


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Sorry this might not be the right section for this topic.


Today (and a few other times recently) we have received an email alert from the PBX saying: "CPU meter shows 55, which is over the threshold of 50. Therefore, a new call has been rejected".


We're running a Hosted environment, running CentOS64, version 5.3.2.


Our server has plenty of processing power and the graphs in the PBX say we're only using 25-30% at max. (image attached)


1. Is the PBX generating false alerts?

2. Is it possible to increase the threshold? (why is it set to only 50%?)

3. What tasks within the PBX use the most CPU load?


Many thanks




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The CPU usage is measured based on statistics for the RTP processing. As will all statistics there are measurement errors that can lead to such errors, but they should be rare. The call rejection also helps to keep existing calls reasonably good. The jitter increases as the CPU load goes up. Unlike in the DSP world, you cannot load up your server until it is 100 % full and all channels are taken. I would say 30 % average load is a sign to think about another server and put new domain on the next server.


You can increase the threshold in the pbx.xml file; originally it was 75 % but we lowered it because in situations like group calls, additional groups can easily spike the CPU. On a large system you can increase it and maybe go to back 75. For small embedded systems like the Vodia mini (Raspberry Pi) I would definitively keep it at 50 %.

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Thank you for the information.


When you say group calls, are you referring to conference calls? We recently have a user that is performing conference calls more often now.


Ideally we would like to keep as many domains and extensions on a single system as possible. We can easily allocate more CPU resources to this server if required.


Do you recommend a limit to the number of domains & users on a single PBX instance in a hosted environment? Or does it not matter as long as there is enough CPU resources?

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ACD and hunt group calls are a problem, especially if they connect to cell phones what have media flowing back and forth. Large groups can easily add 10 call legs to the list for an inbound call.


Yes is it easier to keep everything on one server, and you should do this as long as you can. However it looks like you are approaching the point when you have to throw in more server resources. Once you have the 2nd server running, adding a 3rd one is simple.

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