[LAU] Qtractor MIDI queue timer and TSC

[Rui Nuno Capela]

On 07/30/2018 12:49 PM, Ralf Mardorf wrote:
> Hi,
> 
> by  View > Options... > MIDI tab  I can chose between 'default',
> 'system timer' (for my current installed rt kernels 300Hz), 'HR timer'
> and diverse 'PCM' timers. My old computer doesn't have 'TSC', so
> Qtractor's queue timer still is set to use 'HR timer', to reduce MIDI
> jitter. If I want to chose 'TSC', when running Qtractor on my new
> machine, should there be an entry 'TSC' or since it's the current
> clocksource, would selecting 'default' be the option to use 'TSC'? IOW
> what is 'default' for and why is there no option to select 'TSC'?
> 
> [rocketmouse at archlinux ~]$ cat /sys/devices/system/clocksource/*/available_clocksource
> tsc hpet acpi_pm 
> [rocketmouse at archlinux ~]$ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> tsc
> [rocketmouse at archlinux ~]$ qtractor -v
> qt5ct: using qt5ct plugin
> Qt: 5.11.1
> Qtractor: 0.9.1
> 

those are low-level, read kernel time/clock sources.

instead, the timers that qtractor may use are the high-level ones that
are available through ALSA and only; hrtimer is often the default one
iif the kernel is configured to CONFIG_SND_SEQ_HRTIMER_DEFAULT=y.

you can always check all the available ALSA timers from:
  /proc/asound/timers

the effective current timer in use is listed there, as soon you activate
an ALSA seq queue (eg. qtractor):
  /proc/asound/seq/timer

hth.
cheers
-- 
rncbc aka. Rui Nuno Capela