Subject: Re: [linux-audio-dev] lowish-latency patch and toolchain
From: Juhana Sadeharju (kouhia_AT_nic.funet.fi)
Date: Sat Jul 08 2000 - 18:02:01 EEST
>From: Andrew Morton <andrewm_AT_uow.edu.au>
>
>doing silly things, the scheduling latency is reliably 4 milliseconds on
>a 500MHz machine. Very occasionally reaches 7 millisecs. It has been
Lets talk about 7 ms latency only -- 4 ms is useless information in audio
software which has to be 101% reliable. That is poor compared to earlier
results 2.5 ms. Or can audio input-output latency between A/D & D/A be
somehow less than 7 ms?
>Here's the current DDT list:
>
>- Don't delete huge files (100 megs). There's a hungry
> loop in zap_page_range which has no clear-and-easy fix.
> There _was_ a fix in Ingo's patch, but additional 2.4
> threading has made that unviable.
That is quite important to get fixed. Only perfectionist such as me
would reuse files without deleting them in an audio software. The files
can be very large and very temporary.
I would like to know the most important points of how kernel works,
at what points Ingo added extra scheduling, why it doesn't work now,
why the patch was a kludge. Some simple diagram or pseudo code is fine.
I could take a look at kernel sources if I would like to learn the
advanced stuff at the first course. How your patch changes the diagram?
I would like to help but I have taken only a basic course on kernels.
But I think receiving patches only from one or two person cannot be
a good tactic. It might be better to get more people to understand
the kernel on relevant parts and to think possible solutions.
(I'm reading linux-audio-dev.)
Regards,
Juhana
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