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111 lines
3.8 KiB
111 lines
3.8 KiB
Measuring the SIP channel driver's Performance
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==============================================
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This file documents the methods I used to measure
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the performance of the SIP channel driver, in
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terms of maximum simultaneous calls and how quickly
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it could handle incoming calls.
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Knowing these limitations can be valuable to those
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implementing PBX's in 'large' environments. Will your
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installation handle expected call volume?
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Quoting these numbers can be totally useless for other
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installations. Minor changes like the amount of RAM
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in a system, the speed of the ethernet, the amount of
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cache in the CPU, the CPU clock speed, whether or not
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you log CDR's, etc. can affect the numbers greatly.
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In my set up, I had a dedicated test machine running Asterisk,
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and another machine which ran sipp, connected together with
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ethernet.
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The version of sipp that I used was sipp-2.0.1; however,
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I have reason to believe that other versions would work
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just as well.
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On the asterisk machine, I included the following in my
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extensions.ael file:
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context test11
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{
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s => {
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Answer();
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while (1) {
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Background(demo-instruct);
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}
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Hangup();
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}
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_X. => {
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Answer();
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while (1) {
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Background(demo-instruct);
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}
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Hangup();
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}
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}
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Basically, incoming SIP calls are answered, and
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the demo-instruct sound file is played endlessly
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to the caller. This test depends on the calling
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party to hang up, thus allowing sipp to determine
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the length of a call.
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The sip.conf file has this entry:
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[asterisk02]
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type=friend
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context=test11
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host=192.168.134.240 ;; the address of the host you will be running sipp on
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user=sipp
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canreinvite=no
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disallow=all
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allow=ulaw
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Note that it's pretty simplistic; no authentication beyond the host ip,
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and it uses ulaw, which is pretty efficient, low-cpu-intensive codec.
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To measure the impact of incoming call traffic on the Asterisk
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machine, I run vmstat. It gives me an idea of the cpu usage by
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Asterisk. The most common failure mode of Asterisk at high call volumes,
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is that the CPU reaches 100% utilization, and then cannot keep up with
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the workload, resulting in timeouts and other failures, which swiftly
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compound and cascade, until gross failure ensues. Watch the CPU Idle %
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numbers.
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I learned to split the testing into two modes: one for just call call processing
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power, in the which we had relatively few simultaneous calls in place,
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and another where we allow the the number of simultaneous calls to quickly
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reach a set maximum, and then rerun sipp, looking for the maximum.
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Call processing power is measured with extremely short duration calls:
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./sipp -sn uac 192.168.134.252 -s 12 -d 100 -l 256
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The above tells sipp to call your asterisk test machine (192.168.134.252)
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at extension 12, each call lasts just .1 second, with a limit of 256 simultaneous
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calls. The simultaneous calls will be the rate/sec of incoming calls times the call length,
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so 1 simultaneous call at 10 calls/sec, and 45 at 450 calls/sec. Setting the limit
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to 256 implies you do not intend to test above 2560 calls/sec.
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Sipp starts at 10 calls/sec, and you can slowly increase the speed by hitting '*' or '+'.
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Watch your cpu utilization on the asterisk server. When you approach 100%, you have found
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your limit.
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Simultaneous calls can be measured with very long duration calls:
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./sipp -sn uac 192.168.134.252 -s 12 -d 100000 -l 270
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This will place 100 sec duration calls to Asterisk. The number of simultaneous
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calls will increase until the maximum of 270 is reached. If Asterisk survives
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this number and is not at 100% cpu utilization, you can stop sipp and run it again
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with a higher -l argument.
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By changing one Asterisk parameter at a time, you can get a feel for how much that change
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will affect performance.
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