[ubuntu-studio-devel] Ubuntu Studio 19.10 and Xubuntu 19.04 and dual quad core Xeon E5335 CPUs

Ralf Mardorf ralf.mardorf at alice-dsl.net
Thu Oct 3 13:24:04 UTC 2019

On Thu, 03 Oct 2019 02:41:50 +0000, erich at ericheickmeyer.com wrote:
>The reason it's slower than the generic kernel is that the lowlatency
>kernel prioritizes AUDIO, nothing else.


this is completely irrelevant, if the OP suffers from a regression after
an upgrade.

It has got impact, but in a moment when audio isn't used, it not
necessarily is the cause for bad performance. The combination of the
"lowlatency" kernel settings for example in combination with e.g.
meltdown/spectre mitigations and audit enabled, could make a difference
depending on the kernel version and used hardware. In short, a lot of
factors could affect performance. Troubleshooting by changing rt
priorities, disabling mitigations and audit and a lot of other things,
I can't mention all of them, might lead to some kernel config setting
that maybe lead to a thread handling related regression in the kernel or
even to an issue related to a shared dependency required by LibreOffice
and other software.

For other reasons, manly a regression related to GTK2 apps, I stay with

[weremouse at moonstudio ~]$ lsb_release -a
LSB Version:	core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.6 LTS
Release:	16.04
Codename:	xenial

Ubuntu flavours > 16.04, as well as my "main" Linux (Arch Linux) suffer
from crashing GTK2 GUIs (not from performance issues).

Resume: As soon as "threadirqs" is involved (for the "lowlatency"
kernel it is) even the priorities "feature", could suffer from a
regression and cause issues.

If there is no noticeable performance issue for the OP when using 16.04
with the lowlatency kernel, while for other releases there is such an
issue, _it is_ a regression, even if the generic kernel for
16.04 would allow better performance, than the lowlatency kernel for
16.04, too. The key is, that a machine configured for a special
purpose slowed down after an upgrade and now can't be used anymore,
since the performance isn't good enough anymore.

Assuming the hardware didn't break, then a software related regression
is the reason.

>The generic kernel exists for general purpose, the lowlatency kernel,
>while it works for general use, is definitely configured to prioritize
>lowlatency audio.

But the OP could use the lowlatency kernel of 16.04 for "general
purpose" when using 16.04 and can't continue doing it with newer
releases, so something changed, that shouldn't change. Only this is


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