[asterisk-dev] Asterisk scalability

[Benny Amorsen]

Johansson Olle E <oej at edvina.net> writes:

> With SIP (for some reason, I did not test IAX2 ;-) ) we clearly see
> that the system dies around 1600 simultaneous channels being trashed
> by all the RTP traffic using the p2p rtp bridge. irqbalance fails
> miserably at that point and lack of call quality makes all calls
> sound like the Swedish chef. Unusable is a good description.

> My conclusion so far is the same as Stephen Uhler's at the Atlanta
> Astridevcon - the IP stack is our problem here.

The IP stack itself can only do so much here... At 1600 simultaneous
calls and 20ms packets, that is 80000pps. The ethernet card will do
interrupt mitigation at that point, but AFAIK no ethernet card has any
kind of UDP receive offload.

If you have as many ethernet cards as CPU cores, and you balance the
traffic across the cards, you should in theory get almost perfect
scaling with number of cores (unless Asterisk has problems, but they
can be fixed). If you only have one ethernet card, you
will never go beyond single-core performance -- unless the card does
multiqueue receive, but that is very new so that probably wasn't in
use for your test.


/Benny