I'm working to get the best performance I can out of jackd working with a Tascam US-122. Jack works well with an cheap on-board card (frames/period 64/latency 2.9 mscec), but not so well with the US-122 (and apparently USB sound cards in general). The best frames/period I can run it is 1024 with a lot of xruns. I've got Ingo Molnar's realtime-preempt patch and I'm now attempting to tune the IRQ threads. (My kernel: 2.6.15.2-rt-50studio) (Using modprobe snd_usb_usx2y nrpacks=1) This site describes what I'm trying to do pretty well: http://tapas.affenbande.org/?page_id=6 I intend to tune the IRQ threads so that the usb-interrupt has highest priority. Here are some details: $ lsusb Bus 002 Device 001: ID 0000:0000 Bus 001 Device 002: ID 1604:8007 Tascam US-122 Audio/Midi Interface Bus 001 Device 001: ID 0000:0000 $ cat /proc/interrupts CPU0 CPU1 0: 3832051 0 IO-APIC-edge timer 1: 9522 0 IO-APIC-edge i8042 7: 1 1 IO-APIC-edge parport0 8: 0 0 IO-APIC-edge rtc 9: 0 0 IO-APIC-level acpi 12: 117589 0 IO-APIC-edge i8042 14: 104 0 IO-APIC-edge ide0 50: 614644 0 IO-APIC-level ohci_hcd:usb1 58: 2 0 IO-APIC-level ehci_hcd:usb2 66: 2 0 IO-APIC-level ohci1394 217: 400222 0 IO-APIC-level libata, eth0 225: 290168 0 IO-APIC-level libata, NVidia CK804 233: 0 0 IO-APIC-level libata NMI: 343 202 LOC: 3831594 3831830 ERR: 0 MIS: 0 I've been trying to increase the priority of IRQ 50 (ohci_hcd:usb1) like so: $ chrt -f -p 80 `pidof "IRQ 50"` sched_getscheduler: No such process failed to get pid 80's policy It appears I have a problem getting the pidof any IRQ value. $ echo `pidof "IRQ 0"` $ echo `pidof "IRQ 50"` $ echo `pidof "IRQ 9"` pidof is installed and works...except with the IRQs. I have another concern after reviewing another USX2Y rawusb post from last year. In response to a person having a similar problem as mine, one asked, "Did you set PREEMPT_RT=y (complete real-time) on your kernel configuration? It seems not... otherwise you would see those IRQ threads around." What can I do to verify the existence of the threads? What names do I look for when running top? I don't see any command names with IRQ in them... Thanks, Devin Venable
