There's no such thing as a hard kernel. [sarcasm]But that means Ubuntu was wrong, or they lied! I'm shocked! Everything on the internets is true![/sarcasm] <br><div><br></div><div>Thanks for straitening that out for me. I had emailed the maintainer at Ubuntu but never got a response. (maybe my emails give offensive order because I haven't heard from anyone at RedHat lately either) Sigh... </div><div><br></div><div>I'm bummed to hear that progress on this may be halting. I wish there was someone to bully to get some traction or funding for this. </div><div><br></div><div>Sigh... </div><br><div class="gmail_quote">On Tue Dec 30 2014 at 10:07:47 PM Fernando Lopez-Lezcano <<a href="mailto:nando@ccrma.stanford.edu">nando@ccrma.stanford.edu</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 11/19/2014 08:01 AM, Brian Monroe wrote:<br>
> On Thu Nov 13 2014 at 12:28:27 PM Jeff Sandys <<a href="mailto:jpsandys@gmail.com" target="_blank">jpsandys@gmail.com</a><br>
> <mailto:<a href="mailto:jpsandys@gmail.com" target="_blank">jpsandys@gmail.com</a>>> wrote:<br>
><br>
> Real Time Kernels are available from PlanetCCRMA:<br>
> <a href="http://ccrma.stanford.edu/planetccrma/mirror/fedora/linux/planetcore/20/x86_64/repoview/kernel-rt.html" target="_blank">http://ccrma.stanford.edu/<u></u>planetccrma/mirror/fedora/<u></u>linux/planetcore/20/x86_64/<u></u>repoview/kernel-rt.html</a><br>
><br>
> There are concerns about the implementation of Real Time Kernel as<br>
> expressed in the Musician's Guide:<br>
> <a href="http://docs.fedoraproject.org/en-US/Fedora/15/html/Musicians_Guide/sect-Musicians_Guide-CCRMA_Security_and_Stability.html" target="_blank">http://docs.fedoraproject.org/<u></u>en-US/Fedora/15/html/<u></u>Musicians_Guide/sect-<u></u>Musicians_Guide-CCRMA_<u></u>Security_and_Stability.html</a><br>
><br>
> I am not a systems programmer so I can't speak to these concerns.<br>
> Some of the names of the real time kernel developers listed on the<br>
> PlanetCCRMA kernel-rt page are Red Hat employees.<br>
><br>
> I would like to see Fedora be the premier linux distribution for<br>
> music. But until we can overcome the concerns listed in the<br>
> Musician's Guide we will probably not have a real time kernel in the<br>
> Fedora repositories. Maybe a Fedora "Re-Mix", or Fedora.Next and<br>
> Workstation with the works with Fedora software library may break<br>
> the ice.<br>
><br>
> Well, I think those concerns are why Ubuntu moved to their low-latency<br>
> kernel instead of their kernel-rt. According to their documentation<br>
> (wiki) the lowlatency kernel is a "soft" preempt kernel and the rt<br>
> kernel is "hard' but there's no docs on what make them different, and<br>
> people in channel don't seem to know.<br>
<br>
(sorry for the very late response to this thread - busy busy busy, I<br>
think it is still worth to comment on this)<br>
<br>
Brian, there is no "hard realtime" kernel for Linux. There are only<br>
degrees of latency you can achieve with different combinations of<br>
compile-time options, patching and runtime optimization. All of them are<br>
"soft". You cannot guarantee deadlines on Linux - but you can get pretty<br>
close with a fully optimized system and the RT patch, and if you have<br>
the right hardware.<br>
<br>
I don't know what options Ubunutu uses to build their "low latency"<br>
kernel, I imagine they just enable full preemption and irq threading.<br>
This gives you better latency than a "non-preempt" kernel, but in my<br>
experience that is not enough for realtime audio work with small buffers<br>
(by that I mean jack running at 128x2 or 64x2). YMMV.<br>
<br>
To get really low latencies you need the RT patch (which has stability<br>
issues as has been mentioned in the thread - there are as many testers<br>
as for mainline). To fix those we would need more testers and proper bug<br>
reports that are followed up. But of course that needs kernel gurus that<br>
can respond.<br>
<br>
If you read this article you will see that the future of the RT patch is<br>
not good at this point:<br>
<br>
<a href="http://lwn.net/Articles/617140/" target="_blank">http://lwn.net/Articles/<u></u>617140/</a><br>
<br>
Let's hope this gets better (it is not the first time that the rt patch<br>
has lagged way behind mainline, I think a major rewrite happened in the<br>
Fedora 1 or 2 timeframe and for a while there was nothing new). And BTW,<br>
this is why we are currently stuck at 3.14.x in the Planet CCRMA<br>
kernels, there is nothing newer...<br>
<br>
Sigh...<br>
-- Fernando<br>
<br>
</blockquote></div>