Florin Andrei wrote: > I rebuilt the latest Fedora 2 kernel update to enable preempt and > IO-APIC. > I'm not yet sure about preempt, but IO-APIC has been acting weird. > > It gave me more interrupts (up to 21 instead of 15), but the devices > were distributed suboptimal. > > Without APIC, the nvidia module was alone on its own interrupt, the > EMU10K1 was alone, the ide and eth modules were on separate interrupts, > etc. Quite ok. > > With IO-APIC, nvidia, EMU10K1 and bttv were on the same interrupt, ide2, > ide3 and eth0 were on the same interrupt. > Instead of messing with the kernel again, i just rebooted with the > "noapic" parameter and now the interrupts are looking good again. > > BTW, anyone has any measurements on how bad it is to put essential > devices on the same interrupt? (in terms of xruns) > Please note - The 'optimal' numerical assignment of interrupts with using the APIC model has nothing to do with the older, non-APIC, order. Please do not confuse the idea that 'interrupt #9 is best' with the numbers assigned on an APIC system. These are completely different models. Personally I have done no optimization work on APIC systems and cannot tell you what would be best. However, TTBOMK, there is no simple way today to optimize APIC interrupts in a Linux system anyway, so as far as I can tell you basically take what you get. If you get too many xruns then I guess you go back to non-APIC mode.
