Re: [linux-audio-user] why this works now ...

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Subject: Re: [linux-audio-user] why this works now ...
From: Eric Dantan Rzewnicki (
Date: Fri Sep 10 2004 - 20:00:51 EEST

On Fri, Sep 10, 2004 at 12:42:24AM -0400, Lee Revell wrote:
> On Thu, 2004-09-09 at 23:29, Eric Dantan Rzewnicki wrote:
> Eh, this is how free software works, the concept of wasting people's
> time doesn't mean a lot. I spent a month banging my head against the
> emu10k1 ALSA driver trying to figure out why the latency was 10 times
> worse than in windows. Over a period of weeks I posted 5 or 6 crazy
> theories to alsa-devel, all wrong. Turns out it was just a stupid bug
> where a bunch of instances of SND_PCM_PERIOD_SIZE needed to be changed
> to SND_PCM_PERIOD_BYTES. I submitted a patch and now the latency is
> better than on Windows.
> Moral of the story: in free software, the only person whose time you can
> waste is your own, and it's only wasted time if you don't learn
> anything.

Thanks for the pep talk. :) I did learn a good bit over the past week.
And I'm in a good place to build a lot of different sound tools for
myself now.

> This is very, very important, and also very good news! There have not
> been a lot of reports yet from real linux audio users. So far UP users
> seem to be reporting very good results, while SMP/HT users are still
> seeing weird behavior.
> Can you please try the following so I can report the results to Ingo:
> Run "echo 0 > /proc/sys/kernel/preempt_max_latency"
> Do some audio work for while
> Copy /proc/latency_trace to a file and send it to me via private mail
> Also, once your system seems to be running well, you should disable
> latency tracing with "echo 0 > /proc/sys/kernel/trace_enabled". The
> latency tracer itself can generates latencies of a few ms when it
> updates /proc/latency_trace; this is not reported in the traces.

Thanks for these notes. I'll get the latency trace to you this weekend.

Eric Rz.

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