[asterisk-users] Scaling Asterisk: Dual-Core CPUs not yielding gains at high call volumes

[John Hughes]

Matthew J. Roth wrote:
> Recently, we were pushing our server to almost full CPU utilization. 
> Since we've observed that Asterisk is CPU bound, we upgraded our
> server from a PowerEdge 6850 with four single-core Intel Xeon CPUs
> running at 3.16GHz, to a PowerEdge 6850 with 4 dual-core Intel Xeon
> CPUs running at 3.00GHz.  The software installed is identical and a
> kernel build benchmark yielded promising results.  The new dual-core
> server ran roughly 80% faster, which is about what we expected.
>
> As far as Asterisk is concerned, at low call volumes the dual-core
> server outperforms the single-core server at a similar rate.
Outperforms in what sense?
>   I'm working on a follow-up post that will demonstrate this with some
> benchmarks for a small number of calls in various scenarios on each
> machine.  However, to our surprise as the number of concurrent calls
> increases, the performance gains begin to flatten out.  In fact, it
> seems that somewhere between 200 and 300 calls, the two servers start
> to exhibit similar idle times despite one of them having twice as many
> cores.
What do you mean by "idle" here?