Re: [linux-audio-dev] huge latency peaks with 2.4.10-smp kernel

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Subject: Re: [linux-audio-dev] huge latency peaks with 2.4.10-smp kernel
From: andrew_AT_acooke.org
Date: Thu Oct 18 2001 - 20:28:46 EEST


Hi,

Sorry, this may be somewhat off-topic (please say so and I'll take
this elsewhere). I am considering buying a machine for sound
generation, recording, and midi (for example, recording soft
synthesis, external bass guitar and drum machine in parallel, although
I realise in practice I may have to do complex things in separate
takes and then mix down).

I can afford either dual Athlon 1,2GHz with EIDE disks, or single
Athlon 1,53MHz with SCSI Ultra160 disks. Any idea which would be best
(the post below emphasises the importance of SMP).

Thanks,
Andrew

On Thu, Oct 18, 2001 at 05:04:21PM +0300, Kai Vehmanen wrote:
> Just in case someone is still wondering why we are constantly talking
> about lowlatency kernel patches... Playing an mp3s with ecaplay, running
> as root with sched_fifo scheduling, disk i/o done in a separate i/o
> thread, smp-machine (usually helps to keep latency-peaks down), minor
> system load, I sometimes get the following stats:
>
> (audioio-alsa3) warning! playback underrun - samples lost! Break was at least 8.76 ms long.
> (audioio-alsa3) warning! playback underrun - samples lost! Break was at least 1454.97 ms long.
> (audioio-alsa3) warning! playback underrun - samples lost! Break was at least 2347.27 ms long.
> (audioio-alsa3) warning! playback underrun - samples lost! Break was at least 931.64 ms long.
>
> Engine loop:
> Fastest/slowest/average loop time: 0.4/2364.1/5.9 msec.
>
> Disk i/o loop:
> Fastest/slowest/average loop time: 0.0/3930.2/0.5 msec.
>
> Just compare the avg and max values! This really is quite amazing -
> especially with the usually rock-solid sched-fifo+smp combination.
>
> PS Kernel is standard, non-patched linus-release. Sound driver
> is ALSA 0.9b8 (native-iface).
>
> --
> http://www.eca.cx
> Audio software for Linux!
>
>

-- 
http://www.acooke.org


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