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Date:      Sat, 19 Nov 2022 21:21:44 +0900
From:      Tomoaki AOKI <junchoon@dec.sakura.ne.jp>
To:        Hans Petter Selasky <hps@selasky.org>
Cc:        Alexander Leidinger <Alexander@leidinger.net>, FreeBSD Current <freebsd-current@freebsd.org>
Subject:   Re: ULE realtime scheduler advice needed
Message-ID:  <20221119212144.03c1fbda951b4137b116a6bb@dec.sakura.ne.jp>
In-Reply-To: <c05bf9ad-e436-9479-bfa0-8305a2ea282a@selasky.org>
References:  <20221118091828.Horde.xkZUBiYzzOgubFonR22tMzm@webmail.leidinger.net> <c05bf9ad-e436-9479-bfa0-8305a2ea282a@selasky.org>

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I've  lost track with, but IIRC, someone wrote here, or other ML, or
even forums, kern.sched.preempt_thresh=224 was the default for PC-BSD.

And found some discussion started at [1] on freebsd-stable ML in Apr.
2018.

One more place is at forums [2].

Sorry, not read all of them to confirm.


[1]
https://lists.freebsd.org/pipermail/freebsd-stable/2018-April/088678.html

[2]
https://forums.freebsd.org/threads/general-freebsd-desktop-workload-optimization-thread.21853/



On Sat, 19 Nov 2022 10:28:50 +0100
Hans Petter Selasky <hps@selasky.org> wrote:

> Hi Alexander,
> 
> Thank you for the pointers.
> 
> I will try it out.
> 
> --HPS
> 
> On 11/18/22 09:18, Alexander Leidinger wrote:
> > Quoting Hans Petter Selasky <hps@selasky.org> (from Fri, 18 Nov 2022 
> > 05:47:58 +0100):
> > 
> >> Hi,
> >>
> >> I'm doing some work with audio and have noticed some problems with the 
> >> ULE scheduler. I have a program that generate audio based on 
> >> key-presses. When no keys are pressed, the load is near 0%, but as 
> >> soon as you start pressing keys, the load goes maybe to 80% of a CPU 
> >> core. This program I run with rtprio 8 xxx. The issue I observe or 
> >> hear actually, is that it takes too long until the scheduler grasps 
> >> that this program needs it's own CPU core and stops time-sharing the 
> >> program. When I however use cpuset -l xxx rtprio 8 yyy everything is 
> >> good, and the program outputs realtime audio in-time.
> > 
> > I have something in my mind about ULE not handling idleprio and/or 
> > rtprio correctly, but I have no pointer to a validation of this.
> > 
> >> Or is this perhaps a CPU frequency stepping issue?
> > 
> > You could play with
> > rc.conf (/etc/rc.d/power_profile):
> > performance_cpu_freq="HIGH"
> > performance_cx_lowest="C3"   # see sysctl hw.cpu.0 | grep cx
> > economy_cx_lowest="C3"       # see sysctl hw.cpu.0 | grep cx
> > 
> > Your system may provide other Cx possibilities, and ging to a lower 
> > number (e.g. C1) means less power-saving but faster response from the 
> > CPU (I do not expect that this is causing the issue you have).
> > 
> >> Any advice on where to look?
> > 
> > Potential sysctl to play with to change "interactivity detection" in ULE:
> > https://www.mail-archive.com/freebsd-stable@freebsd.org/msg112118.html
> > 
> > Bye,
> > Alexander.
> > 
> 


-- 
Tomoaki AOKI    <junchoon@dec.sakura.ne.jp>



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