The Hardware: The software: Dell inspiron 5100 Gentoo ~x86 P4 2.4 kernel 2.6.8.1 ingo molnar's VP patch 09 640mb ram kernel 2.6.11-rc4 ingo molnar's RT patch 40gb 7200rpm jackd version 0.99.50 ati radeon m9 alsa lib/drivers 1.0.8 edirol ua-25 USB interface FS filesystem The problem/experience: I'm able to get good low latency performance from kernel 2.6.8.1 ingo molnar's VP patch 09 as described http://www.affenbande.org/~tapas/wiki/index.php?USB%20Low%20Latency% 20Success but with 2.6.11-rcX I'm unable to get any kind of decent low latency performance. Tons of "subgraph timeouts" and "delay of X usecs exceeds..." plus lots of XRUNS. Making the usb IRQs unthreaded in 2.6.11-RT has no effect. At -p 1024 -n 2 jackd runs pretty well, but there's no way I can touch -p 124 -n 3 that I get with 2.6.8.1-VP. The Question: Has ANYONE had success with 2.6.11 and low latency USB? I don't want to keep bashing my head against this if it's just "not ready yet". Also a quick tip: Many of my devices were piled up on IRQ11 (I realize this is not the horrible issue it once was) and I could find no way of getting things moved around (it's a laptop so no card shuffling) and went through a TON of kernel boot options to no effect... till I found acpi_irq_balance. I went from this: 11: 3376988 XT-PIC uhci_hcd, uhci_hcd, uhci_hcd, ehci_hcd, ohci1394, radeon@pci:0000:01:00.0 0/76988 To this: 9: 245868 XT-PIC acpi, radeon@pci:0000:01:00.0 10: 2092423 XT-PIC uhci_hcd, ehci_hcd 11: 1363802 XT-PIC uhci_hcd, uhci_hcd, ath0, ohci1394 Maybe it's a psychological effect but low-latency audio seems a bit more stable now. BTW, I recommend the edirol UA-25 to anyone looking for USB with phantom power, mic pres and midi. (as with any USB device, be prepared to tweak to get performance). Thanks all, -ry -- Ryan Gallagher <ruinaudio@xxxxxxxxxxx>
