Timing 250 versus 1000
No doubt i'm likely to get hammered for asking this on a technical ML, but i'm brave enough and interested enough to risk it.
Is there an important reason why timing in the kernel is set to 250 by default?
I'm using linux to write music with. With the addition of many of the RT patches in the standard kernel, recording audio at low latencies with a standard kernel is no longer a problem, but for those of us who write a lot of midi driven work, we're still more or less required to use some sort of RT kernel to get any degree of playback timing accuracy.
I appreciate my use case is just one among many, but i've done a lot of research on the interlink, and unless i'm missing something really simple here, i can't find a reason why the default timer can't be set at 1000, and be done with it.
I appreciate you chaps are busy, and elbow deep in code, just a "yes it could" or "no we won't" would suffice.
Thanks,
Alex.
Quoted 1 line · Alex Stone
Is there an important reason why timing in the kernel is set to 250 by default?
It's a compromise. Read kernel/Kconfig.hz.
Quoted 3 lines
those of us who write a lot of midi driven work, we're still more or less required to use some sort of RT kernel to get any degree of playback timing accuracy.
The ALSA sequencer timer stopped using the system timer years ago. And the difference between RT and 'normal' kernels is not the timer frequency.
Regards,
Clemens
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Quoted 6 lines · Alex Stone
Quoted 5 lines · Clemens Ladisch
Quoted 3 lines · Alex Stone
those of us who write a lot of midi driven work, we're still more or less required to use some sort of RT kernel to get any degree of playback timing accuracy.
Quoted 6 lines
Quoted 3 lines
The ALSA sequencer timer stopped using the system timer years ago. And the difference between RT and 'normal' kernels is not the timer frequency.
I'm using jack with seq, so are you saying the ALSA sequencer timer is using a higher timer rate than than is set in the kernel,
It's using different timers (RTC or hrtimer), which support higher precision.
Quoted 1 line
and there's no need for me to bother with this,
Yes. If you want to be sure, check that G3 appears in /proc/asound/timers when you're using the sequencer.
Regards,
Clemens
Quoted 14 lines · Clemens Ladisch
Quoted 10 lines · Alex Stone
Quoted 7 lines · Clemens Ladisch
Quoted 3 lines · Alex Stone
those of us who write a lot of midi driven work, we're still more or less required to use some sort of RT kernel to get any degree of playback timing accuracy.
The ALSA sequencer timer stopped using the system timer years ago. And the difference between RT and 'normal' kernels is not the timer frequency.
I'm using jack with seq, so are you saying the ALSA sequencer timer is using a higher timer rate than than is set in the kernel,
It's using different timers (RTC or hrtimer), which support higher precision.
Quoted 7 lines
Quoted 1 line
and there's no need for me to bother with this,
Yes. If you want to be sure, check that G3 appears in
/proc/asound/timerswhen you're using the sequencer.Regards,
Clemens
It does.
Thanks for the info.
Regards,
Alex.