Re: [linux-audio-dev] an open letter to Linus re: low latency

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Subject: Re: [linux-audio-dev] an open letter to Linus re: low latency
From: Erik Steffl (esteffl_AT_pbi.net)
Date: Thu Jun 22 2000 - 03:27:05 EEST


  you have my signature.

        erik

Paul Barton-Davis wrote:
>
> Benno and I hatched a plan to try to get Linus on our side w.r.t. low
> latency. Its not much, but here is a letter I drafted with some input
> from Benno. I invite everyone on this list to "sign it" (i.e. send me
> email telling that you agree to sign it) and/or make suggestions to
> improve it. If you know other people who may want to sign it, please
> get them to contact me to that effect.
>
> I *will* verify with all signatorees that the final version meets
> their approval before sending it on. The version to Linus will be sent
> with email addresses. I plan to also post a version to linux-kernel
> and possibly to slashdot that will NOT include email addresses.
>
> FYI: I plan to try and collect a few names from the VST plugin list as
> well.
>
> --p
>
> ----------------------------------------------------------------------
> Dear Linus,
>
> we are a group of programmers designing, writing and extending audio
> and MIDI applications for Linux. We have no particular affiliation,
> other than all hanging on the linux-audio-dev mailing list, and other
> lists relevant to audio development.
>
> One member of our group, Benno Senoner, did a lot of work last year in
> investigating and documenting problems using Linux for real-time audio
> applications. Others, such as Juhana Sadehaju, had long noted problems
> using Linux for hard disk recording of audio data. Partly as a result
> of Benno's work, Ingo Molnar did a fantastic job of coming up with a
> patch for the 2.2 series that dramatically improved the latencies that
> could be obtained from Linux.
>
> How good? Well, good enough that members of our community who were
> convinced that RTLinux was needed to do a professional job with audio
> changed their minds. Good enough that we were close to (or sometimes
> better than) BeOS, an OS that has had a lot of excellent press in the
> audio world as a replacement for the known-to-be-problematic Windows
> and MacOS systems. Good enough that in some cases, Linux is as good as
> dedicated hardware solutions, offering latencies in the realm of 2-3ms
> for our applications.
>
> There was a lot of excitement that 2.4 might include a version of the
> low latency patches. The excitement came from the possibility that the
> next release of the various distributions of Linux would represent a
> set of "desktops" that were ready for really excellent, "real-time"
> audio and MIDI applications. CPU and disk performance has improved to
> the point where we are on the threshold of a revolution in the way
> that sound synthesis and processing is done, and many of us want to
> ride Linux into the heart of that revolution.
>
> However, it turns out, as best we can gather, that you were not happy
> with the basic structure of some or all of Ingo's low latency
> work. Several of us have defended this position, noting that BeOS got
> their low latencies via carefully designing sections that might
> otherwise block interrupts to not do so. As far as we can tell right
> now, 2.4 will represent more of the same as far as low latency
> limitations, and for us, more of the same means performance much
> *worse* than Windows or MacOS present.
>
> How much worse ? Linux currently offers worst-cases latencies that are
> 10-15 times worse than Windows or MacOS. Developers for those
> platforms still complain about their performance - imagine their
> response to the situation with Linux as it stands today!
>
> We understand that we can always maintain a version of Ingo's low
> latency patch in parallel to the current kernel. But this is not a
> good situation for us. We would like to persuade several companies
> that produce applications and API's for audio+MIDI work to make their
> code, designs and programs available for Linux. We would like to be
> able to produce our own "real-time" applications and not have to tell
> users (who will likely know nothing about Linux, or computers in
> general) that they need to patch their kernel before using
> them. Neither of these goals are realistic given the current state of
> low latency support in the emerging 2.4.
>
> We would like to know:
>
> * what are your general feelings on modifying Linux to support
> the kind of applications we are concerned with ?
>
> * what kinds of compromises, if any, you might accept in order
> to get good low latency performance into the kernel sooner,
> rather than later ?
>
> * what design goals you have in mind when you talk about
> doing low latency "right", rather than "wrong, as in
> Ingo's approach" ?
>
> Thank you for your consideration, for Linux and your benign dictatorship.
>
> Paul Barton-Davis
> Benno Senoner


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