Andrew Kohlsmith wrote: > On Friday 30 July 2004 19:51, Mike Benoit wrote: >> Tuning these [PCI latencies] should allow you to give your TDM cards >> long burst lengths, and make your IDE devices very premptable... > > I would have figured you want very short burst lengths to prevent any one > device from hogging the PCI bus and delaying your VOIP data. IIRC the VOIP > traffic is very short anyway (1000 interrupts a second, 8 bit PCM data or > 64 bytes of actual VOIP data (sampled at 8000Hz, that's 8 8 bit samples > every > interrupt) each way... I think.
Yes, but by lowering the available time that another device can tie up the PCI bus, you increase the chances that your TDM cards get their interrupts handled very quickly. And since you know that your TDM card interupts are very short (but very frequent), you want a way to prioritize them. So shorten the burst lengths everything else is allowed, and allow your TDM card to tie up the bus whenever it wants. Working with the 2.6 kernel and some of the new stuff by Ingo Molnar, you can actually get interrupt priorities, and the possibility of allowing specific RT threads preempting "lower priority" interrupts. Basically, to give Asterisk ideal conditions to to echo cancel, you want to make sure that: 1) PCI bus is given to TDM card as soon as possible when it wants to raise an interrupt. 2) Make sure you OS can handle the interrupt soon enough. Use #1 to tune PCI latencies (yes, an IDE or Network event can tie up your PCI bus for many usec, delaying your TDM interrupts). For #2, you have to live with linux-2.4 being "good enough", but if your willing to live on the edge, do check out some of the new recent work that's going on around 2.6, mainly driven by the pro-audio users. On a 600Mhz Eden, users are reporting 42us latencies on RT user-space threads. Basically working out to the almost theoretical minimum hardware capabilities. Again - none of these will guarantee asterisk echo-cancel/dropouts will be fixed, but the all work towards giving asterisk the best conditions for it to do what it is trying to do. _______________________________________________ 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 _______________________________________________ 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