[LAD] Jackd & Real Time Kernel

[Benny Alexandar]

Hi Len,

I'm using  jackdmp 1.9.12.  I checked the file /etc/security/limits.d/audio.conf, and is
named as audio.conf.disabled. How to enable this ?

When I run my jack client standalone program, I could see the prints as follows,

------------------
jackdmp 1.9.12

JACK server starting in realtime mode with priority 10
self-connect-mode is "Don't restrict self connect requests"
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer little-endian
ALSA: use 2 periods for playback
Cannot use real-time scheduling (RR/10)(1: Operation not permitted)
AcquireSelfRealTime error
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
JACK server started
Cannot use real-time scheduling (RR/5)(1: Operation not permitted)
JackClient::AcquireSelfRealTime error
-----------------------------------

-ben



________________________________
From: Len Ovens <len at ovenwerks.net>
Sent: Friday, January 12, 2018 10:27 PM
To: Benny Alexandar
Cc: linux-audio-dev at lists.linuxaudio.org
Subject: Re: [LAD] Jackd & Real Time Kernel

On Fri, 12 Jan 2018, Benny Alexandar wrote:

> I just compiled simple_client.c and things starts to work.
> My doubt is do I need to install linux real-time kerel update for JACK.

It depends... personally, I use the lowlatency kernel with no problems
using an ice1712 based PCI card audio interface. Your situation may
differ.

> How do I know if jack is running real time, is it by checking for xruns ?

Jack runs in real time mode by default. If you are running jackd2 (version
1.9*) then check ~/.log/jack/jackdbus.log

for the line:
Thu Dec 28 10:38:26 2017: JACK server starting in realtime mode with
priority 10

Otherwise the same line will appear in jackd terminal output when started.

Do note that part of the jackd instalation process sometimes gets missed
by some installers. There should be a file
/etc/security/limits.d/audio.conf If this is missing or named as disabled,
you may not be able to get jackd to start in realtime mode. The two lines
of importance in that file are:
@audio   -  rtprio     95
@audio   -  memlock    unlimited
  Depending on your distro the group may be other than audio. Whatever that
group is, your user needs to be a part of it. Most audio distributions get
this right already (even ubuntustudio), but non-audio distros generally
need this to be fixed. After adding yourself to the audio (or whatever)
group you will need to logout and back in before that will have any
effect.

--
Len Ovens
www.ovenwerks.net<http://www.ovenwerks.net>

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