hi all,
As Brian stated, in the early UbuntuStudio releases a rt kernel was delivered by default, but then they moved to lowlatency
it sounds interesting, i'll be glad to contribute in some way, even if i'm not a developer. personally i guess that a low latency kernel fits most of the use cases, but it would be definitely interesting working on this.. according to my limited knowledge on this topics, the current kernel should be "near" lowlatency:
here's my (default) config
grep CONFIG_PREEMPT /boot/config-$(uname -r)
# CONFIG_PREEMPT_RCU is not set
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
grep CONFIG_HZ /boot/config-$(uname -r)
# CONFIG_HZ_PERIODIC is not set
# CONFIG_HZ_100 is not set
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
CONFIG_HZ_1000=y
CONFIG_HZ=1000
here's my (default) config
grep CONFIG_PREEMPT /boot/config-$(uname -r)
# CONFIG_PREEMPT_RCU is not set
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
grep CONFIG_HZ /boot/config-$(uname -r)
# CONFIG_HZ_PERIODIC is not set
# CONFIG_HZ_100 is not set
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
CONFIG_HZ_1000=y
CONFIG_HZ=1000
probably, as a first step, it would be good to compile the kernel with CONFIG_PREEMP=y
i've applied the recommendations given by QuickScan, but still having "not good" for limits.conf even though the new limits should be fetched from /etc/security/limits.d/95-jack.conf .
i'm not finding the cpugovernors, probably they're not compiled in the kernel and it would be worth to give it a try (AVLinux gives the chance to set up those from the panel)
i'm not finding the cpugovernors, probably they're not compiled in the kernel and it would be worth to give it a try (AVLinux gives the chance to set up those from the panel)
As Brian stated, in the early UbuntuStudio releases a rt kernel was delivered by default, but then they moved to lowlatency
according to the kernel archives, the latest rt patch is for 3.14...
2014-11-13 22:39 GMT+01:00 Be Ing <be.0@xxxxxxx>:
One of the reasons I'd like to see a realtime (and/or low-latency) patched version of Linux in Fedora is to keep it more up-to-date than Planet CCRMA. The latest release in the CCRMA repo at the moment is 3.14 whereas the current stable version of Linux in Fedora Updates is 3.16 and 3.17 is in testing. I don't think being behind a week or two in updates would be a big deal, but being behind 3 releases of Linux is.
I have no experience with RPM or creating & maintaining other packages, but I have been considering learning so I can contribute to Fedora. I am willing to help with maintaining a realtime and/or low-latency kernel package, but I think someone with more experience maintaining packages should be at the lead of this.
I have also been thinking about packaging a Linux-libre realtime kernel for Freedora (http://www.fsfla.org/ikiwiki/selibre/linux-libre/freed-ora.en.html ). Having an up-to-date realtime kernel in the Fedora repos would facilitate that.
Regarding the security and stability concerns, yes, those are real concerns. Albeit rarely, I have had a few issues with some misbehaving program (I think Firefox or Chromimum, not sure though) locking the whole system when running the Planet CCRMA kernel for normal desktop use, so I only boot into the Planet CCRMA kernel when I need to. I am not sure, but I don't think the low-latency kernel that is default in Ubuntu Studio has the same issues. Hopefully someone more knowledgable can chime in. If no one knows, we could test out how Ubuntu Studio runs, although I probably won't have much time to do so for a few weeks. We could do what Ubuntu Studio does and package a low-latency kernel as default in Fedora Jam and also have a realtime kernel package in the repositories. I'm not sure what exactly is different between the generic and low-latency kernels, but I don't think it would be too difficult to figure that out by looking at the Ubuntu packages. They have a wiki page explaining the different kernels they package: https://help.ubuntu.com/community/UbuntuStudio/RealTimeKernel
>Sent: Thursday, November 13, 2014 at 2:28 PM
>From: "Jeff Sandys" <jpsandys@xxxxxxxxx>
>To: music@xxxxxxxxxxxxxxxxxxxxxxx
>Subject: Re: Low Latency vs. Real Time Kernel - actual latencies ?
>
>Hello Fedora musicians, I've been lurking this list for a little bit and this is my first time chiming in on something.
>
>I think it is important to pursue an official realtime kernel for Fedora. I think a distribution focused on audio without a realtime kernel would have a serious bug, that IMO, would be worth delaying publication for.
>...
>
>Real Time Kernels are available from PlanetCCRMA:
> http://ccrma.stanford.edu/planetccrma/mirror/fedora/linux/planetcore/20/x86_64/repoview/kernel-rt.html
>
>There are concerns about the implementation of Real Time Kernel as expressed in the Musician's Guide:
> http://docs.fedoraproject.org/en-US/Fedora/15/html/Musicians_Guide/sect-Musicians_Guide-CCRMA_Security_and_Stability.html[http://docs.fedoraproject.org/en-US/Fedora/15/html/Musicians_Guide/sect-Musicians_Guide-CCRMA_Security_and_Stability.html]
>
>I am not a systems programmer so I can't speak to these concerns. Some of the names of the real time kernel developers listed on the PlanetCCRMA kernel-rt page are Red Hat employees.
>
>I would like to see Fedora be the premier linux distribution for music. But until we can overcome the concerns listed in the Musician's Guide we will probably not have a real time kernel in the Fedora repositories. Maybe a Fedora "Re-Mix", or Fedora.Next and Workstation with the works with Fedora software library may break the ice.
>-- Jeff
>_______________________________________________ music mailing list music@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/music[https://admin.fedoraproject.org/mailman/listinfo/music]
>Sent: Thursday, November 13, 2014 at 10:59 AM
>From: "Brian Monroe" <briancmonroe@xxxxxxxxx>
>To: "Be Ing" <be.0@xxxxxxx>, music@xxxxxxxxxxxxxxxxxxxxxxx
>Subject: Re: Low Latency vs. Real Time Kernel - actual latencies ?I think so too, thanks for chiming in.
>
>I'm still waiting to get into the packagers group, but I have a koji account and theoretically could compile an rt kernel. I think the standard naming schema in other distros is kernel-rt. It should be only adding a few lines to the spec file to enable the rt kernel, but when you look at how many kernel update there are for Fedora every week, I'm not sure as to how up to date we'll be able to keep up due to the work load. We're already are down on developers, and people like Brandon are keeping us afloat.
>
>Are we going to be ok as a project to be behind a week or two in Kernel releases? Personally I'm for more stable kernels when it comes to music production vs. having the latest and greatest, but I also think that should be a clearly indicated as a feature
>
>That being said, I feel strongly as though others should take this task on, if not me, then someone else or better yet, a few of us.
>
>
>I'm looking into the Ubuntu Studio and turns out they dropped the RT kernel as default. They're using a "lowlatency" kernel instead of a rt kernel (though they do still supply an rt kernel but not by default). I do know that users are able to get 1.5 ms latency with zero xruns so I'm guessing they're doing something other than real-time scheduling, I just don't know what. Thoughts?
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