First of all, I just wanted to say how super happy I am about having lowlatency built-in to the Generic kernel and that we are going to be removing the lowlatency kernel from future kernel releases. However, this does cause some questions and leaves Ubuntu Studio in a state of ambiguity when it comes to the kernel.
I do wish the kernel team would have told me that the lowlatency kernel was planned to be sunset prior to 24.04’s release so that we could have planned accordingly, especially considering the HWE stack. Speaking of which, and I’m assuming here that the HWE kernels will not have a lowlatency variant since they’re, for all intents and purposes, backports of what lands in later Ubuntu releases. Is this going to be the case?
Right now, the plan, due to the HWE stack and assuming there is no lowlatency kernel going forward, is to reconfigure livecd-rootfs so that our Noble images so that they use the generic kernel for 24.04.1 and forward, and to reconfigure our ubuntustudio-lowlatency-settings package so that our default kernel parameters not only include threadirqs but also preempt=full and nohz_full=all which is rather trivial.
So, please let me know, and I hope to have better communication with the kernel team in the future.
Hi @eeickmeyer, we (kernel team) are sill planning to support lowlatency for 24.04, same with the backported HWE kernels based on 24.04 that will have a lowlatency variant. Did you see any comment / message that is stating the opposite or am I missing something? Thanks for pointing this out.
Now that in 24.04 all linux-lowlatency configuration options have migrated to settings or merged with linux-generic, there is no need for a distinct linux-lowlatency binary any more and eventually will be deprecated.
It would make sense that the lowlatency kernel would be deprecated with this, but now it seems as though there’s a conflict in messaging because now I’m really confused.
The LinkedIn post does sound confusing. The key takeaway for me is “eventually”. I can imagine that’s something on the roadmap towards 24.10 (or later), and doesn’t (yet) affect 24.04.X. Like you, I hope this roadmap will be communicated in timely fashion.
@eeickmeyer that post was worded a bit vaguely. it should have read ‘and eventually will be deprecated in a future release of Ubuntu’. we would never make such a drastic change in a released stable kernel. this was just the initial notice that there is no reason to maintain 2 distinct binaries any more and we will eventually, in some future release of Ubuntu, do something to consolidate, but how and when is yet TBD
My concern is that, as I understand it, the HWE kernels are usually a 1:1 backport of the kernel from the later release, for instance 24.10’s kernel would be the HWE-a kernel, 25.04’s kernel would be the HWE-b kernel, and so on.
With that in mind, it would validate my concern that one of those later kernels would not have the lowlatency binary built. That said, I might not know the picture here or the complete engineering behind how or what is being done here.
While I do understand that the 6.8 lowlatency kernel will not disappear, one of the later HWE kernels, which would be the default for a later point release update, could potentially not have the lowlatency kernel, in which case a SRU to both livecd-rootfs and ubuntustudio-lowlatency-settings would be needed.
Ubuntu Studio is committed to a 3-year LTS period with support ending in April 2027. While I understand these kernel support concerns are TBD, I would like to keep these communication channels open so that if and when something is decided, I can know as soon as possible.
Just wanted to thank you for your work with Ubuntu Studio, and mention that I was able to enable the HWE kernel stack on my Ubuntu Studio “24.04.2 LTS” installation. For those interested in HowTo info, skip to section with bold header below.
For me enabling the HWE stack seems to have fixed a few intermittent issues I previously had suspending my laptop to both sleep and hibernation states. Also seems to have vastly increased hibernation speed, and resulted in a ridiculous increase in performance for the screen saver I use (xscreensaver) on KDE. No doubt kernel video fixes and upgrades to MESA are helping a lot with this.
I did run into a few issues getting this to work, but found it easy to configure using info supplied in your post above to enable low-latency on the generic HWE kernel. The main problem I ran into was the following error when I tried to enable the lowlatency HWE stack:
swilson@stuBuntu:~$ sudo apt-get install --install-recommends linux-lowlatency-hwe-24.04
[sudo] password for swilson:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
linux-lowlatency-hwe-24.04 : Depends: lowlatency-kernel but it is not installable
E: Unable to correct problems, you have held broken packages.
Now I don’t have complete understanding of either the kernel or apt package manager (in fact far from it ), but it does seem as if the ability to install the HWE kernel stack for lowlatency kernels on 24.04 has been disabled somewhere along the line.
For anybody looking to do this, the steps I took to enable low-latency within the generic HWE kernel on the Ubuntu Studio platform were:
Ran “sudo apt install --install-recommends linux-generic-hwe-24.04”.
Modified the “/etc/default/grub.d/ubuntustudio.cfg” file like thus:
swilson@stuBuntu:~$ cat /etc/default/grub.d/ubuntustudio.cfg`
# Activate lowlatency effects of kernel
### SDW - Added last 2 kernel boot options for low-latentcy in generic HWE kernel
GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT threadirqs preempt=full nohz_full=all
# Make sure lowlatency kernel is default in grub menu if other flavours are installed
### SDW - Disabled line below to enable generic HWE kernel
#GRUB_FLAVOUR_ORDER="lowlatency $GRUB_FLAVOUR_ORDER"
Ran “sudo update-initramfs -c -k all”.
Ran “sudo update-grub”.
Rebooted the system.
Now I also like to reboot into “multi-user.target” whenever I make changes like this to give me an out if they fail. Won’t bother detailing all of that. So far I am really happy using the upgraded generic kernel. Hope this post helps someone.
Hi @swilson62, thank you for reporting your experience with the low-latency kernel!
The HWE kernel stack for the lowlatency kernel is still supported. In 24.04, for the 6.14 HWE kernel we had a recent change in how the lowlatency kernel is built and configured, which now requires the additional lowlatency-kernel package to configure the boot parameters. This new package was unfortunately out-of-sync with the linux-generic-hwe-24.04 update, which caused the apt dependency issue you reported. Sorry for the inconvenience.
We have just released the lowlatency-kernel package in noble-updates and it should be synced across all archive mirrors in the next couple of hours. Can you please try again to install linux-generic-hwe-24.04 and report whether that fixes your issue?
Thanks for letting me know about that! Initially got the same failure when trying to install linux-lowlatency-hwe-24.04. Just tried again after waiting a couple more hours, and now it will allow the install without any errors.
Decided to abort the install, and continue using the generic kernel with the command line boot parameter modifications shown in my comment above. It’s still working great with the generic kernel, and I’m fairly certain those parameters are all that is needed for Ubuntu Studio to work well.
Did test Ardour audio capture, and if anything the new kernel has improved capture. Also I feel like the generic kernel will likely get a higher priority going forward with updates, as it should. I continue to be amazed at how well the kernel team keeps up with all the updates to the kernel, and stand behind anything to make your jobs easier.
For the record, linux-lowlatency-hwe-24.04 [1] is just a meta package that depends on the generic HWE 6.14 kernel plus lowlatency-kernel which fiddles with the kernel commandline. Kernel-wise, HWE 6.14 lowlatency and HWE 6.14 generic and Plucky 6.14 are all the same (except that the HWE kernels are compiled using Noble’s toolchain).
), but it does seem as if the ability to install the HWE kernel stack for lowlatency kernels on 24.04 has been disabled somewhere along the line.