Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch
From: Lee Revell (rlrevell_AT_joe-job.com)
Date: Wed Jul 21 2004 - 09:03:12 EEST
On Wed, 2004-07-21 at 01:30, Ingo Molnar wrote:
> * Andrew Morton <akpm_AT_osdl.org> wrote:
>
> > > discovered I can reliably produce a large XRUN by toggling Caps Lock,
> > > Scroll Lock, or Num Lock. This is with 2.6.8-rc1-mm1 + voluntary
> > > preempt
> >
> > That's odd. I wonder if the hardware is sick. What is the duration is the
> > underrun? The info you sent didn't include that.
>
> no, it's the ps2 driver that is sick. The ps2 keyboard driver is one of
> the few places that busy-polls for IRQ completion from within a tasklet
> context for things like led switching (yuck) - this can cause many
> millisecs delays on all boards i tried.
>
I can also add that La Monte H. P. Yarroll's patch to daemonize softirqs
seems to provide major improvements in latency (does not help this
problem of course). There has been at least one other patch posted to
LKML that that does the same thing. Will this feature be in the kernel
anytime soon?
Lee
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