limits.conf nice rtprio

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limits.conf nice rtprio

Jaromír Mikeš-2
Hi,

I am afraid that I still don't understand limits.conf file properly.
Hopefully someone can explain me some details.
I have limits.conf file like this:

@mira - rtprio 99
@mira - memlock 8000000
@mira - nice -10

@mira    /usr/bin/jackd              nice=-1 rtprio=85
@mira    /usr/bin/qjackctl           nice=-1 rtprio=84
@mira    /usr/bin/ardour            nice=-1 rtprio=83
@mira    /usr/bin/hydrogen           nice=-1 rtprio=82
@mira    /usr/bin/jackeq             nice=-1 rtprio=81
@mira    /usr/bin/jack-rack          nice=-1 rtprio=80
.
.

Should I do something better with nice and rtprrio values to ensure better RT robustness ?
There is also possible add "priority" value in limits.conf file ... Should I use it?

2nd question:
In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
How it is connected with these above? Should be used?

mira

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Re: limits.conf nice rtprio

Paul Davis
OMFG.

How many years have to go by before people stop thinking that nice values have anything to do with this?

http://jackaudio.org/faq/linux_rt_config.html


On Thu, Aug 17, 2017 at 10:34 AM, Jaromír Mikeš <[hidden email]> wrote:
Hi,

I am afraid that I still don't understand limits.conf file properly.
Hopefully someone can explain me some details.
I have limits.conf file like this:

@mira - rtprio 99
@mira - memlock 8000000
@mira - nice -10

@mira    /usr/bin/jackd              nice=-1 rtprio=85
@mira    /usr/bin/qjackctl           nice=-1 rtprio=84
@mira    /usr/bin/ardour            nice=-1 rtprio=83
@mira    /usr/bin/hydrogen           nice=-1 rtprio=82
@mira    /usr/bin/jackeq             nice=-1 rtprio=81
@mira    /usr/bin/jack-rack          nice=-1 rtprio=80
.
.

Should I do something better with nice and rtprrio values to ensure better RT robustness ?
There is also possible add "priority" value in limits.conf file ... Should I use it?

2nd question:
In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
How it is connected with these above? Should be used?

mira

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Re: limits.conf nice rtprio

Ralf Mardorf
In reply to this post by Jaromír Mikeš-2
Hi,

I guess the nice values are null and void, IOW IIUC they don't affect
anything [1], at least for cosmetical reasons remove it from your
limits.conf. If you fear that something could become unresponsive, you
could decrease "rtprio 99" to a lower value. I never did it myself, but
some users do so.

To optimize real-time performance you should start with using Rui's
script rtirq [2]. There are other things to improve real-time
capability, often setting the cpu frequency scaling governor to
performance improves a lot [3]. There are additional useful
opportunities, e.g. unbinding USB devices that share an IRQ with the
audio device could be helpful, but a lot of hints provided by the
Internet are plain nonsense. The most important thing to consider is
choosing the appropriate kernel. For some tasks it's useful to build a
rt patched kernel [4]. The so called "lowlatency" kernels provided by
Ubuntu flavours gains you more or less nothing. If you should use a
mainline kernel, simply add "threadirqs" to the boot parameters, for
syslinux it does look like e.g. this

$ grep thread /boot/syslinux/syslinux.cfg -B1 -A1
LABEL Threadirqs
    MENU LABEL Arch Linux ^threadirqs
    LINUX ../vmlinuz-linux
    APPEND root=LABEL=archlinux ro threadirqs
    INITRD ../initramfs-linux.img

I prefer using real-time patched kernels. If you should use external
MIDI equipment there are other things to consider, too, special jackd
settings, e.g. for jack 2 the "-X alsarawmidi" switch and that using USB
MIDI much likely does cause much more MIDI jitter compared to game port
MIDI and PCI/PCIe MIDI.

Regards,
Ralf

[1]
"Contrary to a lot of misinformation on the web, there is no reason to
include a line here that provides enhanced “niceness” control, which is
completely irrelevant for realtime scheduling and low latency audio
applications." - http://jackaudio.org/faq/linux_rt_config.html

[2]
http://www.rncbc.org/jack/

[3]
echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor >/dev/null

To see the status run

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

to get back "powersave" or "ondemand" run

echo powersave | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor >/dev/null
     ^^^^^^^^^
resp. replace "powersave" with "ondemand"

[4]
https://www.kernel.org/pub/linux/kernel/projects/rt/
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Re: limits.conf nice rtprio

Ralf Mardorf
In reply to this post by Jaromír Mikeš-2
On Thu, 17 Aug 2017 16:34:56 +0200, Jaromír Mikeš wrote:
>@mira - memlock 8000000

Oops, I missed this one.

To fix this, take a look at the link to the jack FAQ I already posted.
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Re: limits.conf nice rtprio

Ralf Mardorf
In reply to this post by Paul Davis
On Thu, 17 Aug 2017 11:00:45 -0400, Paul Davis wrote:
>OMFG.
>
>How many years have to go by before people stop thinking that nice
>values have anything to do with this?

Novices much likely follow one of the uncountable wrong "hints" provided
by the Internet.

Others and I don't have the time to fix "pro-audio" Wikis we are
allowed to edit, they usually don't provide the nice value mistake,
but much other misinformation or completely irrelevant info, e.g.
related to pulseaudio usage for pro-audio. Paul, feel free to fix those
Wikis and request to delete the uncountable wrong "hints" nobody could
access to edit them.
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Re: limits.conf nice rtprio

Jaromír Mikeš-2
In reply to this post by Ralf Mardorf


2017-08-17 17:17 GMT+02:00 Ralf Mardorf <[hidden email]>:
Hi,

I guess the nice values are null and void, IOW IIUC they don't affect
anything [1], at least for cosmetical reasons remove it from your
limits.conf. If you fear that something could become unresponsive, you
could decrease "rtprio 99" to a lower value. I never did it myself, but
some users do so.

To optimize real-time performance you should start with using Rui's
script rtirq [2]. There are other things to improve real-time
capability, often setting the cpu frequency scaling governor to
performance improves a lot [3]. There are additional useful
opportunities, e.g. unbinding USB devices that share an IRQ with the
audio device could be helpful, but a lot of hints provided by the
Internet are plain nonsense. The most important thing to consider is
choosing the appropriate kernel. For some tasks it's useful to build a
rt patched kernel [4]. The so called "lowlatency" kernels provided by
Ubuntu flavours gains you more or less nothing. If you should use a
mainline kernel, simply add "threadirqs" to the boot parameters, for
syslinux it does look like e.g. this

Thanks Paul and Ralf for wiping old this old myth I was living in ;)

What about my 2nd question?
In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
It corresponds to -P cli option
For what is it good and how it should be used?

mira


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Re: limits.conf nice rtprio

Paul Davis


On Thu, Aug 17, 2017 at 11:57 AM, Jaromír Mikeš <[hidden email]> wrote:

What about my 2nd question?
In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
It corresponds to -P cli option
For what is it good and how it should be used?

​It's under "Advanced". That means ... if you don't know what it does, don't use it, or adjust it. ​

 


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Re: limits.conf nice rtprio

Ralf Mardorf
In reply to this post by Jaromír Mikeš-2
On Thu, 17 Aug 2017 17:57:30 +0200, Jaromír Mikeš wrote:
>Thanks Paul and Ralf for wiping old this old myth I was living in ;)
>
>What about my 2nd question?
>In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
>It corresponds to -P cli option
>For what is it good and how it should be used?

Hi Mira,

I was against the new QjackCtl GUI. The fundamental idea of this tab
design is, that users should only use the "Parameters" tab and just in
exceptional cases, experts should use the "Advanced" tab.

Don't care about this option, neither use it via QjackCtl, nor as a
command line option.

$ man jackd | grep "\-realtime" -A2 | head -14 | tail
       -R, --realtime
              Use realtime scheduling (default = true). This is needed for reliable low-latency performance.  On many systems, it requires jackd to run with special scheduler and memory
              allocation privileges, which may be obtained in several ways.
--
       -r, --no-realtime
              Do not use realtime scheduling.

       -P, --realtime-priority int
              When running --realtime, set the scheduler priority to int.

Regards,
Ralf
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Re: limits.conf nice rtprio

Jaromír Mikeš-2


2017-08-17 18:19 GMT+02:00 Ralf Mardorf <[hidden email]>:
On Thu, 17 Aug 2017 17:57:30 +0200, Jaromír Mikeš wrote:
>Thanks Paul and Ralf for wiping old this old myth I was living in ;)
>
>What about my 2nd question?
>In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
>It corresponds to -P cli option
>For what is it good and how it should be used?

Hi Mira,

I was against the new QjackCtl GUI. The fundamental idea of this tab
design is, that users should only use the "Parameters" tab and just in
exceptional cases, experts should use the "Advanced" tab.

Don't care about this option, neither use it via QjackCtl, nor as a
command line option.

$ man jackd | grep "\-realtime" -A2 | head -14 | tail
       -R, --realtime
              Use realtime scheduling (default = true). This is needed for reliable low-latency performance.  On many systems, it requires jackd to run with special scheduler and memory
              allocation privileges, which may be obtained in several ways.
--
       -r, --no-realtime
              Do not use realtime scheduling.

       -P, --realtime-priority int
              When running --realtime, set the scheduler priority to int.

Clear!

thank you ;)

mira


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Re: limits.conf nice rtprio

Ralf Mardorf
In reply to this post by Paul Davis
On Thu, 17 Aug 2017 12:05:46 -0400, Paul Davis wrote:
>It's under "Advanced". That means ... if you don't know what it does,
>don't use it, or adjust it.

I never liked Rui's new QjackCtl GUI.

If you want to access advanced settings for Firefox, you can't access
them via the regular menu, you need to use a quasi hidden
option named "about:config".

If you want to use "about:config" you are warned and first need to
"accept the risk".

Providing an "Advanced" tab right beside the "Parameters" tab is more an
invitation to try out those advanced parameters, than a user-friendly
pointer.

A sign "Keep off the grass!" results in more people stepping on your
lawn, than no sign at all.
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Re: limits.conf nice rtprio

Will Godfrey
In reply to this post by Paul Davis
On Thu, 17 Aug 2017 12:05:46 -0400
Paul Davis <[hidden email]> wrote:

> On Thu, Aug 17, 2017 at 11:57 AM, Jaromír Mikeš <[hidden email]>
> wrote:
>
> >
> > ​
> > What about my 2nd question?
> > In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
> > It corresponds to -P cli option
> > For what is it good and how it should be used?
> >  
>
> ​It's under "Advanced". That means ... if you don't know what it does,
> don't use it, or adjust it. ​

I find that response surprising, unhelpful and quite wrong.

How can anyone discover whether they need to use a feature if nobody will tell
them what it does?
How does one become 'advanced'?

--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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Re: limits.conf nice rtprio

Hermann Meyer


Am 17.08.2017 um 19:40 schrieb Will Godfrey:

> On Thu, 17 Aug 2017 12:05:46 -0400
> Paul Davis <[hidden email]> wrote:
>
>> On Thu, Aug 17, 2017 at 11:57 AM, Jaromír Mikeš <[hidden email]>
>> wrote:
>>
>>> ​
>>> What about my 2nd question?
>>> In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
>>> It corresponds to -P cli option
>>> For what is it good and how it should be used?
>>>  
>> ​It's under "Advanced". That means ... if you don't know what it does,
>> don't use it, or adjust it. ​
> I find that response surprising, unhelpful and quite wrong.
>
> How can anyone discover whether they need to use a feature if nobody will tell
> them what it does?
> How does one become 'advanced'?
>

Me to, for example, running jack with the default priority of "10" is
somewhat unsuccessful that I never understand this default value. I turn
it to 85 to make it useful at all.

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Re: limits.conf nice rtprio

Paul Davis
In reply to this post by Will Godfrey
When you've spent years dealing with people screwing up their JACK installations/configurations by messing with parameters which were never really meant to be exposed to users, you will definitely be "Advanced".

Maybe there are other ways to get there.

On Thu, Aug 17, 2017 at 1:40 PM, Will Godfrey <[hidden email]> wrote:
On Thu, 17 Aug 2017 12:05:46 -0400
Paul Davis <[hidden email]> wrote:

> On Thu, Aug 17, 2017 at 11:57 AM, Jaromír Mikeš <[hidden email]>
> wrote:
>
> >
> > ​
> > What about my 2nd question?
> > In qjackctrl Settings -> Advanced ... there is a "Priority" option ...
> > It corresponds to -P cli option
> > For what is it good and how it should be used?
> >
>
> ​It's under "Advanced". That means ... if you don't know what it does,
> don't use it, or adjust it. ​

I find that response surprising, unhelpful and quite wrong.

How can anyone discover whether they need to use a feature if nobody will tell
them what it does?
How does one become 'advanced'?

--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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Re: limits.conf nice rtprio

Ralf Mardorf
On Thu, 17 Aug 2017 13:59:29 -0400, Paul Davis wrote:

>On Thu, Aug 17, 2017 at 1:40 PM, Will Godfrey wrote:
>> How can anyone discover whether they need to use a feature if nobody
>> will tell them what it does?
>> How does one become 'advanced'?
>When you've spent years dealing with people screwing up their JACK
>installations/configurations by messing with parameters which were
>never really meant to be exposed to users, you will definitely be
>"Advanced".
>
>Maybe there are other ways to get there.

That's scorn, isn't it? The advanced tab shows e.g. "H/W monitor". The
smart novice reading the jackd man page, reads

$ man jackd | grep "\-hwmon" -A1
       -H, --hwmon
              Enable hardware monitoring of capture ports.  This is a method for obtaining "zero latency" monitoring of audio input.  It requires support in hardware and from the under‐
--
              Presently (March 2003), only the RME Hammerfall series and cards based on the ICE1712 chipset (M-Audio Delta series, Terratec, and others) support --hwmon.  In the future,
              some consumer cards may also be supported by modifying their mixer settings.
--
              Without --hwmon, port monitoring requires JACK to read audio into system memory, then copy it back out to the hardware again, imposing the basic JACK system latency deter‐
              mined by the --period and --nperiods parameters.

If I wouldn't know better, I would guess that it requires usage of
"--hwmon" to do hardware monitoring with my RME Hammerfall HDSPe AIO.
The next step would be to guess that all the advanced options might be
required to optimise performance and to get access to all features
provided by the hardware.

I'm a power user helping a lot of people with audio related issues on
several mailing lists, editing audio related Wikis, if the time allows
this, even was asked to take over Arch Audio and something like the
following still happens from time to time.

On Thu, 17 Aug 2017 19:57:51 +0200, Hermann Meyer wrote:
>Me to, for example, running jack with the default priority of "10" is
>somewhat unsuccessful that I never understand this default value. I
>turn it to 85 to make it useful at all.

I'm using jackd since around a decade and never used this option. What
becomes more successful, if I use it? I'll test it ASAP ;).

I suspect that it could be true what Hermann mentions. I simply don't
know and at least need to test it, since there is no manual providing
information. Even a default value isn't mentioned by jack 2's help or
its man page.

Regards,
Ralf
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Re: limits.conf nice rtprio

Fons Adriaensen-3
In reply to this post by Paul Davis
On Thu, Aug 17, 2017 at 01:59:29PM -0400, Paul Davis wrote:

> parameters which were never really meant to be exposed to users

then the at least the defaults should be OK. They usually are not.

Ciao,

--
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: limits.conf nice rtprio

Paul Davis
I've never adjusted any of the parameters that are now on that tab in more than a decade.

There has never been a pull request or a bug report suggesting new defaults.


On Thu, Aug 17, 2017 at 3:21 PM, Fons Adriaensen <[hidden email]> wrote:
On Thu, Aug 17, 2017 at 01:59:29PM -0400, Paul Davis wrote:

> parameters which were never really meant to be exposed to users

then the at least the defaults should be OK. They usually are not.

Ciao,

--
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: limits.conf nice rtprio

Ralf Mardorf
On Thu, 17 Aug 2017 15:48:18 -0400, Paul Davis wrote:

>On Thu, Aug 17, 2017 at 3:21 PM, Fons Adriaensen wrote:
>> On Thu, Aug 17, 2017 at 01:59:29PM -0400, Paul Davis wrote:
>>  
>> > parameters which were never really meant to be exposed to users  
>>
>> then the at least the defaults should be OK. They usually are not.
>>
>I've never adjusted any of the parameters that are now on that tab in
>more than a decade.
>
>There has never been a pull request or a bug report suggesting new
>defaults.

Why should somebody suggest new defaults? The values could be
adjusted, if required and QjackCtl provided most jack parameters, if not
all in a single tab, before it was split into two tabs. Much
likely LTS release distros still provide the old version of QjackCtl,
let alone that jack's defaults provided by package maintainers could
vary, I've seen configurations with --clients=foo
--ports-per-application=bar.
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Re: limits.conf nice rtprio

Jaromír Mikeš-2


2017-08-17 22:10 GMT+02:00 Ralf Mardorf <[hidden email]>:
On Thu, 17 Aug 2017 15:48:18 -0400, Paul Davis wrote:
>On Thu, Aug 17, 2017 at 3:21 PM, Fons Adriaensen wrote:
>> On Thu, Aug 17, 2017 at 01:59:29PM -0400, Paul Davis wrote:
>>
>> > parameters which were never really meant to be exposed to users
>>
>> then the at least the defaults should be OK. They usually are not.
>>
>I've never adjusted any of the parameters that are now on that tab in
>more than a decade.
>
>There has never been a pull request or a bug report suggesting new
>defaults.

Why should somebody suggest new defaults? The values could be
adjusted, if required and QjackCtl provided most jack parameters, if not
all in a single tab, before it was split into two tabs. Much
likely LTS release distros still provide the old version of QjackCtl,
let alone that jack's defaults provided by package maintainers could
vary, I've seen configurations with --clients=foo
--ports-per-application=bar.

The reason I started this topic is that I bought new USB sound card Focusrite 2i2.
But I am not happy with latency 15-20ms is not fine for simple task I am using it.
Just running japa to check RTA.
Periods/Buffer 3, deadline scheduler, scaling_governor performance

Just trying figure out if I can make somewhat better.

mira

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Re: limits.conf nice rtprio

Ralf Mardorf
Hi Mira,

is it a 1st Gen or 2nd Gen?

I've got a 18i20 2nd Gen, -n 2 -p 128 works with my outdated Athlon
and now with my Celeron without issues. IOW even my new machine hasn't
got much horsepower.

If irqbalance should be enabled, disable it. Did you already test
different USB ports?

What's the output of

  /path/to/rtirq status

?

The path were rtirq is installed unfortunately isn't the same for all
distros.

/etc/init.d/rtirq status
/etc/rc.d/rtirq status

or just /usr/bin/rtirq, if so you could run

rtirq status

What kernel are you using?

uname -a

Regards,
Ralf
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Re: limits.conf nice rtprio

David Jones
In reply to this post by Jaromír Mikeš-2



On Aug 17, 2017 12:08, Jaromír Mikeš <[hidden email]> wrote:

>
>
>
> 2017-08-17 22:10 GMT+02:00 Ralf Mardorf <[hidden email]>:
>>
>> On Thu, 17 Aug 2017 15:48:18 -0400, Paul Davis wrote:
>> >On Thu, Aug 17, 2017 at 3:21 PM, Fons Adriaensen wrote:
>> >> On Thu, Aug 17, 2017 at 01:59:29PM -0400, Paul Davis wrote:
>> >>
>> >> > parameters which were never really meant to be exposed to users
>> >>
>> >> then the at least the defaults should be OK. They usually are not.
>> >>
>> >I've never adjusted any of the parameters that are now on that tab in
>> >more than a decade.
>> >
>> >There has never been a pull request or a bug report suggesting new
>> >defaults.
>>
>> Why should somebody suggest new defaults? The values could be
>> adjusted, if required and QjackCtl provided most jack parameters, if not
>> all in a single tab, before it was split into two tabs. Much
>> likely LTS release distros still provide the old version of QjackCtl,
>> let alone that jack's defaults provided by package maintainers could
>> vary, I've seen configurations with --clients=foo
>> --ports-per-application=bar.
>
>
> The reason I started this topic is that I bought new USB sound card Focusrite 2i2.
> But I am not happy with latency 15-20ms is not fine for simple task I am using it.
> Just running japa to check RTA.
> Periods/Buffer 3, deadline scheduler, scaling_governor performance
>
> Just trying figure out if I can make somewhat better.
>
> mira

And to think all I did to get my cheap USB sound card to work at 5-10ms latency was install a low-latency kernel (from KXStudio) and change buffer and period settings on QJackCtl's non-Advanced settings tab.

That's on two different systems: one Intel i7, the other an AMD Phenom 2. No tweaking deadline scheduler or scaling governor (for the Intel, Phenom 2 has no such capability).

But I'm using Debian Testing + KXStudio, not ArchLinux or Ubuntu.

David W. Jones
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authenticity, honesty, community
http://dancingtreefrog.com
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