> -------- Snip -------- > 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?
Yes, Speex is pretty cpu intensive compared to other codecs. The best perfoming codecs are g.711u/a, gsm and g.729 in that order. > 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? With top you can increase the number of seconds beteween refreshes. this will give you a better useage over time. but if your cpu is spiking too 100% or even over 75% using the default update of 3 seconds your codec or your free memory may be the problem. Codec transcoding can take some serious hits on memory. > > 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? _______________________________________________ Asterisk-Users mailing list [email protected] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
