[Jack-Devel] How does --hwmon work?

Ralf Mardorf ralf.mardorf at alice-dsl.net
Sat May 6 20:04:48 CEST 2017

On Sat, 06 May 2017 19:15:02 +0200, David Kastrup wrote:
>Ralf Mardorf <ralf.mardorf at alice-dsl.net> writes:
>> RME does not support Linux by themselves, so even if they made
>> something possible, there is no support.  
>So what do you call "support" that is available for other operating

They provide drivers and the audio interfaces mixer software by
themselves. The only other OS I'm using is iOS. Actually I need to use
class compliant audio interfaces for the iPad, there are no drivers
available at all and even not all class compliant audio interfaces work
with iOS, even not when using an active USB hub, to get rid of power
issues, caused by some audio interfaces, resp. by the iOS limit of
allowed poser consumption.

>> [rocketmouse at archlinux ~]$ hwinfo --cpu|grep Mo|sort -u
>>   Model: 6.60.3 "Intel(R) Celeron(R) CPU G1840 @ 2.80GHz"
>> [rocketmouse at archlinux ~]$ hwinfo --memory|grep Si
>>   Memory Size: 7 GB + 512 MB  
>Well, my specs are 2.5GHz Penryn and 4GB of memory (extending memory to
>8GB with DDR2 SODIMM would be about as expensive as the whole computer
>was, and for audio recording it would not appear to make a difference).
>Bottlenecks are more likely bus speed (800MHz I think, but with the RAM
>connected with 667MHz) than anything else.  And current kernels.

Hey, we agree in at least one point. IMO 4 GiB of RAM are usually
enough, even for resource hungry audio productions. I increased the RAM
to 8 GiB to compile software in tmpfs, still not enough to compile
Firefox :D.

Actually it doesn't matter, if you and I agree or disagree regarding
the hardware monitoring, since you much likely need to find a way to
get as close as possible to your needs, with what is available.

One way would be to optimize everything to get as low as possible
latency, to use software monitoring.

You mentioned "current kernels". Rt patched? A more or less vanilla
kernel with or without "threadirqs"?

The last time I made music, I used 4.9.13-rt12. "persianrug" and
"pussytoes" are just mnemonics I added myself, the kernels are vanilla
with unimportant patches, resp. just one important patch, the rt patch.
Without the rt-patch, but with threadirqs, the latency is one frames
value less good, IOW instead of 128, I need to use 256 frames.

I didn't make music with 4.10.13 and 4.9.20-rt16, since I was
successfully job hunting. 

[rocketmouse at archlinux ~]$ pacman -Q linux linux-rt-persianrug linux-rt-pussytoes
linux 4.10.13-1
linux-rt-persianrug 4.9.13_rt12-1
linux-rt-pussytoes 4.9.20_rt16-1
[rocketmouse at archlinux ~]$ grep threadirqs /boot/syslinux/syslinux.cfg -A1
    MENU LABEL Arch Linux ^threadirqs
    LINUX ../vmlinuz-linux
    APPEND root=LABEL=archlinux ro threadirqs
    INITRD ../initramfs-linux.img

Apart from the kernel other tuning might have positive impact, too.
E.g. unbinding USB devices sharing an IRQ with the audio interface not
necessarily improves latency, but it could do so.

How much latency would please you? Would 5 ms for monitoring still be
too much latency?


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