Re: Renicing for OpenGL smoothness.

Re: Renicing for OpenGL smoothness.

[Notifications]

> So I was thinking, maybe some of you could inform me, which processes  
> are involved in getting the graphics on-screen.
> I have already started making a renicing script.

Well, there's just two processes that I couldn't find information on  
online though, kintegrityd and kworker. I set them to highpri for the  
moment, in my script. However the script didn't seem to make much of a  
difference, so the processes that run on Ubuntu Natty Narwhal seems to be  
quite well behaved. It's just a principle though, that any background  
processes shouldn't be able to request a lot of cpu, while I am running my  
opengl app. I do see that the ubuntu folks have reniced some processes of  
their own though.
[khelper] [kintegrityd] [kblockd] [kacpid] [kacpi_notify] [kacpi_hotplug]  
[ata_sff] and more are all at -20. Seems to be quite the opposite of what  
I am doing...

Possible bug, with extreme low latency audio.

[Uwaysi Bin Kareem]

Hello.

I have shaved a kernel for features I suspected to add to os-jitter, to  
get the lowest possible latency from it.
The kernel is 2.6.36-zen0
The .config is http://www.paradoxuncreated.com/tmp/.config

What happens is, if I set my audioapp, (renoise) to extremely low  
latencies, (96khz, 8 samples buffers x 2), the audio seems to be  
distorting and speeding up, while having periods of normal playback.

With other kernel configurations, I have just experienced, glitches, which  
is typical of buffer underruns.
This kernel config though, reduces the overall os-jitter, so I could push  
the latency much lower. However then I stumbled on this problem.

Best Regards,
Uwaysi.

Re: Possible bug, with extreme low latency audio.

[Clemens Ladisch]

Uwaysi Bin Kareem wrote:
> I have shaved a kernel for features I suspected to add to os-jitter, to
> get the lowest possible latency from it.
> 
> What happens is, if I set my audioapp, (renoise) to extremely low
> latencies, (96khz, 8 samples buffers x 2), the audio seems to be
> distorting and speeding up, while having periods of normal playback.

I'd guess that buffer is so small that it's smaller than the DMA FIFO
and/or the DMA burst size of the sound device (whatever it is) so that
the DMA controller is not able to accurately report the current position
in the buffer.

Obviously, the lowest possible latency is higher than 167 µs.


Regards,
Clemens

Renicing for OpenGL smoothness.

[Uwaysi Bin Kareem]

Hiya. I'm sitting here playing some OpenGL games, and thinking, isn't it  
rude of processes demanding the same amount of cpu, when I am here,  
wanting the smoothest possible OpenGL experience.

So I am renicing. But my knowledge of the kernel is limited. So I was  
thinking, maybe some of you could inform me, which processes are involved  
in getting the graphics on-screen.

I have already started making a renicing script.

---

highpri=-20;
lowpri=19;
for pid in `pgrep ""`; do renice -n $lowpri -p $pid; done #ubuntu runs a  
lot of processes that can be put in the background.
for pid in `pgrep "init"`; do renice -n $highpri -p $pid; done #probably  
good to have high priority?
for pid in `pgrep "kthreadd"`; do renice -n $highpri -p $pid; done #does  
drivers or anything else create kernel threads that are involved in the  
graphics on-screen?
for pid in `pgrep "ksoftirq"`; do renice -n $highpri -p $pid; done #surely  
these are?
for pid in `pgrep "X"`; do renice -n $highpri -p $pid; done
for pid in `pgrep "metacity"`; do renice -n $highpri -p $pid; done
for pid in `pgrep "hd-audio0"`; do renice -n $highpri -p $pid; done

--
Comments and information appreciated.