[arch-proaudio] Changes to jack/jack2 and realtime privileges
Hi all, as announced before [1], recent changes to the jack and jack2{,-dbus} packages (now in [extra] and [community] respectively) have made the previously shipped configurations obsolete and decoupled the audio group from acquiring realtime privileges by default when installing jack. The package realtime-privileges [2] has been created to serve as the new way of achieving this by the means of a dedicated 'realtime' group, to which users, that need the settings, must be added. It is now an optional dependency to jack and jack2{,-dbus} and can of course also be dependend upon from other packages if needed. In theory, this change shouldn't mean much of a difference to users, that need realtime (just install realtime-priviliges and add your user to the realtime group: `gpasswd -a <user> realtime`), while it doesn't have any consequences for users that have no use for it to begin with. Best, David [1] https://lists.archlinux.org/pipermail/arch-proaudio/2018-July/000163.html [2] https://www.archlinux.org/packages/community/any/realtime-privileges/ -- https://sleepmap.de
On Tue, 21 Aug 2018 23:43:26 +0200, David Runge wrote:
It is now an optional dependency to jack and jack2{,-dbus} and can of course also be dependend upon from other packages if needed.
Hi, it's reasonable to change the group name from "audio" to "realtime", since regular usage of CNC machines has less to do with audio and they are even not much used for industrial music. However, wasn't the original plan to tidy up Arch pro-audio step by step and among other things, to stay away from esoteric? What's the advantage of 'rtprio 98' over upstream's recommendation 'rtprio 99'? The packages URL is even more confusing. The package: [rocketmouse@archlinux community-any]$ cat 99-realtime-privileges.conf @realtime - rtprio 98 @realtime - memlock unlimited [rocketmouse@archlinux community-any]$ grep url PKGBUILD url="https://wiki.archlinux.org/index.php/Realtime_process_management" Upstream: "@realtime - rtprio 99 @realtime - memlock unlimited" - http://jackaudio.org/faq/linux_rt_config.html The package's URL: "An example for why one might want to alter these settings is to get high-performance audio working. The defaults are permissive enough to get jack-server running with hydrogen or ardour. However, for higher performance audio applications it might be necessary to redefine the values for rt_prio from 65 to 80 or even higher! The following settings work well with ardour: @audio - rtprio 70 @audio - memlock 250000" - https://wiki.archlinux.org/index.php/Realtime_process_management#Configuring... I prefer to stay with my manual edited settings... [rocketmouse@archlinux community-any]$ tail -2 /etc/security/limits.conf @audio - rtprio 99 @audio - memlock unlimited ...perhaps I'll migrate to a group "realtime", too. What are the below rules good for? [rocketmouse@archlinux community-any]$ cat 40-realtime-privileges.rules # rw access to /dev/cpu_dma_latency to prevent CPUs from going into idle state KERNEL=="cpu_dma_latency", GROUP="realtime" # rw access to /dev/rtc0 KERNEL=="rtc0", GROUP="realtime" # rw access to /dev/hpet0 KERNEL=="hpet", GROUP="realtime" For example, using hpet without such a rule seemingly works without issues: [rocketmouse@archlinux community-any]$ grep -i hpet /usr/lib/udev/rules.d/*; echo $? 1 Regards, Ralf -- pacman -Q linux{,-rt{-pussytoes,-cornflower,,-securityink}}|cut -d\ -f2 4.18.3.arch1-1 4.18_rc8_rt1-1 4.16.18_rt12-1 4.16.18_rt11-1 4.16.18_rt10-1
On Wed, 22 Aug 2018 12:23:37 +0200 Ralf Mardorf <ralf.mardorf@alice-dsl.net> wrote:
On Tue, 21 Aug 2018 23:43:26 +0200, David Runge wrote:
It is now an optional dependency to jack and jack2{,-dbus} and can of course also be dependend upon from other packages if needed.
What's the advantage of 'rtprio 98' over upstream's recommendation 'rtprio 99'?
That's very simple. At 99 there are some kernel management threads running, like the watchdogs, the ones responsible to move tasks from one CPU to another, etc. Best not to interfere with that.
The packages URL is even more confusing.
Yes the wiki pages are going to need a serious haircut at some point.
What are the below rules good for?
40-realtime-privileges.rules # rw access to /dev/cpu_dma_latency to prevent CPUs from going into idle state
This one is quite clear, no? Not available on all CPUs
# rw access to /dev/rtc0 # rw access to /dev/hpet0
AFAIK, these are useless on a modern kernel like ours. I would like to see them removed.. -- Joakim
On Wed, 22 Aug 2018 13:26:09 +0200, Joakim Hernberg wrote:
Yes the wiki pages are going to need a serious haircut at some point.
Somebody might want to verify those changes: https://wiki.archlinux.org/index.php?title=Realtime_process_management&type=revision&diff=536793&oldid=496758 https://wiki.archlinux.org/index.php?title=Professional_audio&type=revision&diff=536791&oldid=528716
participants (3)
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David Runge
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Joakim Hernberg
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Ralf Mardorf