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    SubjectRe: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch
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    On Mon, 2004-07-12 at 19:31, Andrew Morton wrote:
    > Lee Revell <rlrevell@joe-job.com> wrote:
    > >
    > > On Sun, 2004-07-11 at 01:25, Andrew Morton wrote:
    > > > What we need to do is to encourage audio testers to use ALSA drivers, to
    > > > enable CONFIG_SND_DEBUG in the kernel build and to set
    > > > /proc/asound/*/*/xrun_debug and to send us the traces which result from
    > > > underruns.
    > > >
    > >
    > > OK, here goes. The following traces result from running JACK overnight
    > > like so, on an otherwise idle system. Hardware is a VIA EPIA 6000, with
    > > a 600Mhz C3 processor. Kernel is 2.6.7 + volunatary_preempt patch.
    > > voluntary_preempt and kernel_preemption are both on.
    > >
    > > jackd -v --realtime -d alsa --outchannels 2 --rate 48000 --shorts
    > > --playback --period 32 --nperiods 2
    > >
    > > These settings require less than 666 microseconds scheduler latency.
    > > The average performance is quite good - 5-20 *microseconds*!
    >
    > OK, thanks. The problem areas there are the timer-based route cache
    > flushing and reiserfs.
    >
    > We can probably fix the route caceh thing by rescheduling the timer after
    > having handled 1000 routes or whatever, although I do wonder if this is a
    > thing we really need to bother about - what else was that machine up to?
    >

    Gnutella client. Forgot about that. I agree, it is not reasonable to
    expect low latency with this kind of network traffic happening. I am
    impressed it worked as well as it did.

    > resierfs: yes, it's a problem. I "fixed" it multiple times in 2.4, but the
    > fixes ended up breaking the fs in subtle ways and I eventually gave up.
    >

    Interesting. There is an overwhelming consensus amongst Linux audio
    folks that you should use reiserfs for low latency work. Should I try
    ext3?

    Lee





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