On Tue, 2004-09-28 at 18:05, Mark Knecht wrote: > Lee Revell wrote: > > On Tue, 2004-09-28 at 16:11, Mark Knecht wrote: > >>Lee Revell wrote: > >>>I get no xruns at 32 (!) frames using 2.6 with the VP patches, > >>>and my soundcard shares an interrupt with USB: > >>> > >> > >>(Non-argumentive if it's unclear) Please stick a USB mouse on the USB > >>port that is shared and wiggle it madly while doing some of this. Can > >>you create an xrun? > >>> > > > > No, this does not cause an xrun, because even though the USB interrupt > > handler interrupts the soundcard irq (and vice versa), it does not run > > for a significant fraction of the period time. Of course it's best to > > have the soundcard on an interrupt that is not shared. But whether that > > interrupt is #5 or #10 does not matter. > > Great. Just checking. (You did *actually* do it, right?) ;-) Ok, I repeated this test just now (I had actually done it, but weeks ago). It does not make a difference at all if I plug the mouse into the front USB port (shared with the soundcard) or the rear one (not shared). This is with the soundcard and mouse on different IRQs: load = 1.3880 max usecs: 7.000, spare = 659.000 load = 1.2195 max usecs: 7.000, spare = 659.000 load = 1.1353 max usecs: 7.000, spare = 659.000 load = 1.8439 max usecs: 17.000, spare = 649.000 <-- start moving mouse load = 1.6727 max usecs: 10.000, spare = 656.000 load = 2.3379 max usecs: 20.000, spare = 646.000 load = 2.5954 max usecs: 19.000, spare = 647.000 <-- stop moving mouse load = 1.8983 max usecs: 8.000, spare = 658.000 load = 1.4747 max usecs: 7.000, spare = 659.000 load = 1.2629 max usecs: 7.000, spare = 659.000 Here is the mouse and soundcard sharing an IRQ: load = 1.2021 max usecs: 8.000, spare = 658.000 load = 1.2017 max usecs: 8.000, spare = 658.000 load = 1.2014 max usecs: 8.000, spare = 658.000 load = 1.8770 max usecs: 17.000, spare = 649.000 <-- start moving mouse load = 2.4400 max usecs: 20.000, spare = 646.000 load = 2.7215 max usecs: 20.000, spare = 646.000 load = 2.7121 max usecs: 18.000, spare = 648.000 <-- stop moving mouse load = 1.9567 max usecs: 8.000, spare = 658.000 load = 1.5789 max usecs: 8.000, spare = 658.000 load = 1.3901 max usecs: 8.000, spare = 658.000 So, the interrupt response is about a microsecond faster with them on different IRQs. This is what I expected (but I did not expect it to show up in jackd -v!). And, regardless of whether the interrupt is shared, mouse activity will only delay jackd by about 20 microseconds. These numbers all support my original point that tweaking your interrupts is a waste of time, you should be installing a low latency kernel instead... rlrevell@mindpipe:~$ uname -r 2.6.9-rc2-mm3-VP-S6 Lee
