[Asterisk-Users] Erratic CPU load

[Eric Giesselbach]

> -----Original Message-----
> From: Zoa [mailto:zoachien at securax.org]
> Sent: Tuesday, March 29, 2005 1:59 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] Erratic CPU load
> 
> 
> Hi,
> Im the astertest guy.
> If you are referring to the graphs on page 41 - 42, please note that
> those are done on a embedded via 800mhz cpu and not on a 
> system similar
> to yours. So i'm pretty sure you can do more than 10 speex 
> encodings at
> the same time. (also some things changes since we did those 
> tests, some
> optimizations and configuration options were done to the speex codec
> implementation in asterisk. Now you can choose your own quality vs cpu
> usage balance on asterisk)
> 
> I suggest you go to cvs-head and check out the changes to the 
> speex codec.

I did test a IAX/Speex connection between two test machines with cvs head installed. They also showed bursty cpu usage, but max cpu usage during the bursts might be lower, I'll check again. And I didn't change any speex config options, so there's hope :)

> Without changes to your asterisk machine, i estimate you will 
> be able to
> do around 30 to 40 channels on your machine if it was without zaptel.
> Zaptel does not take a lot cpu especially compared to speex encodings.
> (i know from experience)
> 
> About the periodic load, please see if any calls are being 
> setup or tear down, or specific applications are used in those cases.

30 channels would be great. Enough to service the 30 ISDN (E1) channels. 
The periodic load was not due to call setup or tear down, and as far as I could see (ps, top) there were no processes getting in Asterisk's way. Zaptel "on it's own" gave low (and steady) load during a test with calls from PSTN via TE110P to MOH on the gateway itself. But I guess only a test with iax, with codec translation and *without* zap can rule out zap as part of the cause. 

> 
> Saddly enough, i still didnt find the time to do any load measurements
> on pri cards. Although i have a test setup ready to go.

I can continue testing using your hints, thanks.

Eric.



> 
> Zoa.
> 
> 
> Eric Giesselbach wrote:
> 
> >Hi,
> >
> >During tests with a IAX2/PSTN gateway I've been getting 
> strange results for processor idle time and load. I 
> (re)search(ed) this issue for a while, but I didn't get any 
> good explainations. Can somebody help me?
> >
> >I have several sites that rely on a central server for 
> connection to the PSTN. Calls to the PSTN are routed over the 
> Internet to this PSTN gateway using IAX2 in trunk mode. To 
> minimize bandwith usage, the Speex codec is used. The central 
> PSTN gateway is a P4 3.0GHz, 1GByte mem, has a TE110P card 
> supporting ISDN30 and runs Asterisk version 1.0.3 on Debian Sarge.
> >
> >While sustaining 5 connections dialed in through the TE110P 
> (terminated at remote sites through IAX) and running top on 
> the PSTN gateway, I see 98% CPU idle time most of the time. I 
> also see short (around 10sec) bursts of high CPU usage 
> (40-50%) by one of the asterisk processes supporting the 
> connection. The bursts happen in irregular intervals, ranging 
> from 30 to 60 sec. Meanwhile, the reported average load jumps 
> up and down between 0.1 to 0.7.
> >
> >What's happening here? Is the processor load really this 
> erratic, or am I looking at an artefact in cpu usage 
> measurement? Maybe there is an aliasing effect caused by the 
> periodic cpu load (20ms, default trunk frequency) and the cpu 
> usage measurement (also periodic?), but I don't know how to 
> check this. If this top reading is an artefact, is there a 
> way to check the actual (realtime) load?
> >
> >Regarding the actual processor usage for speex encoding: 
> this report suggests my processor is indeed quite busy 
> encoding a few speex channels: 
> http://astertest.com/astricon_performance.ppt. Given the 
> results in this report, I doubt the PSTN gateway will support 
> more than 10 speex encodings. At the same time, the same 
> processor encodes 756x756 PAL television to mpeg-4 on my 
> mythtv box at home. Twice, leaving room for scheduled jobs. 
> Has anyone some references to documentation to put these 
> figures into perspective?
> >
> >Thanks in advance,
> >Eric.
> >
> >_______________________________________________
> >Asterisk-Users mailing list
> >Asterisk-Users at lists.digium.com
> >http://lists.digium.com/mailman/listinfo/asterisk-users
> >To UNSUBSCRIBE or update options visit:
> >   http://lists.digium.com/mailman/listinfo/asterisk-users
> >
> >
> 
>