[asterisk-users] Is there real benefits on a SMP machine for Asterisk?

[Tzafrir Cohen]

On Fri, Oct 12, 2007 at 05:29:24PM +0200, Philipp Kempgen wrote:
> Atis Lezdins wrote:
> 
> > I have 8-core system that has web interface + sql + java + some other stuff 
> > running, and at 30 simultenous calls i get loadavg maximum of 3.
> 
> I wouldn't be too happy about a system with a
> loadavg of 3.

The loadavg is the average number of threads[0] ready to run (or running).
In your typical desktop system it is 0, because the CPU is mostly idle.

But why do we care so much about the load average? We are all well
familiar with a single CPU and single core systems. In those systems
only one thread can execute at each time. If the load average is greater
than 1 it means that there on the average[1] at least one process
waiting for the CPU and not getting executed immediately. Maybe one 
thread of Asterisk uses the CPU and another thread is waiting for it.

So what we really want to know is if a certain thread of Asterisk was
waiting in the run queue too long. Asterisk should not need to wait when
presented with a voice frame to move around. Is there any more direct
way of checking that?

[0] Recall that the CPU executes threads, regardless to which process
they belong. Two different threads of he same process and two different
processes are the same for this discussion.

[1] There are three different loadavg numbers: for the last minute, for
the last five minutes and for the last 15 minutes. 

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               Tzafrir Cohen       
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