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<p>Oh great news! I installed the kernel following the instructions
on the wiki:
<a class="moz-txt-link-freetext" href="https://fedoraproject.org/wiki/Test_Day:2022-01-23_Kernel_5.16_Test_Week">https://fedoraproject.org/wiki/Test_Day:2022-01-23_Kernel_5.16_Test_Week</a></p>
<p>Now, how do I configure Pipewire to get realtime priority without
needing to manually run chrt? The Pipewire documentation is
unclear...
<a class="moz-txt-link-freetext" href="https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2024">https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2024</a></p>
<p>If we could get preempt=full and Pipewire with realtime priority
by default in upstream Fedora, that would be wonderful. Just plug
and play for realtime audio... well, I can dream.<br>
</p>
<div class="moz-cite-prefix">On 1/24/22 16:10, Nils Tonnätt wrote:<br>
</div>
<blockquote type="cite" cite="mid:OWI86R.X29ZXIWCM4IQ1@posteo.de">
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<div>Hi,</div>
<div><br>
</div>
<div>I checked out the upcoming kernel for Fedora 35:</div>
<div><br>
</div>
<div>
<div>[ 0.069100] Kernel command line:
BOOT_IMAGE=(hd2,gpt2)/boot/vmlinuz-5.16.2-200.fc35.x86_64
root=UUID=7812bc02-a2ea-4335-bc7b-636e1612841a ro rhgb quiet
threadirqs preempt=full</div>
<div>[ 0.069632] Dynamic Preempt: full</div>
</div>
<div><br>
</div>
<div>This week is kernel test week. So probably next week, we
will have a kernel with dynamic preemption in Fedora.</div>
<div><br>
</div>
<div>Best,</div>
<div>Nils</div>
<div><br>
</div>
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Am Di, 11. Jan 2022 um 17:55:04 -0800 schrieb Fernando
Lopez-Lezcano <a class="moz-txt-link-rfc2396E" href="mailto:nando@ccrma.Stanford.EDU"><nando@ccrma.Stanford.EDU></a>:<br>
<blockquote type="cite">
<div class="plaintext" style="white-space: break-spaces;">On 1/10/22 3:06 PM, Fernando Lopez-Lezcano wrote:
...
<blockquote>==== System A: kernel 5.14.8-200.1.motu.fc34.ccrma (preempt=full)
</blockquote>
I did a local build for fc34 of the latest Koji 5.16.0 Fedora source package and installed it in my "System B". At least in that source package CONFIG_PREEMPT_DYNAMIC is set to "y" (yay!, cross fingers it stays that way!) and I can switch to preempt=full when booting without any further tweaks.
The kernel no longer prints the status when booting, but "cat /sys/kernel/debug/check/preempt" confirms the system is in preempt=full state.
The latency numbers I see on my first test and reported by cyclictest are not quite as good as "System A" (running 5.14.8), but they are good.
-- Fernando
PS: Anyone knows how to convince pipewire to let go of an audio interface? That is, not use it anymore? I'm trying the Motu driver and I would like to remove the snd_usb_audio kernel driver to reload the motu driver - long story of why, and it is not easy as the driver is in use by pipewire...
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