Re: audio dropouts still
Hi,
perhaps one of the maintainers mentioned at
http://packages.debian.org/wheezy/linux-image-rt-686-pae could add a few
notes.
On Wed, 2014-01-15 at 12:21 +1100, Zenaan Harkness wrote:
> I installed the latest 3.12-1-rt-amd64 (rt) kernel, with dist-upgrade
> and reboot of course.
>
> Reading some of the links provided in this thread, I note that
> Debian's -rt kernel has:
> CONFIG_HZ_250=y
> # CONFIG_HZ_300 is not set
> # CONFIG_HZ_1000 is not set
> CONFIG_HZ=250
This might be ok if the new full no HZ features are used and unlikely
will have impact to audio. For MIDI still hr timer/hpet does provide a
much higher resolution than just 1000 Hz, it's 1000000000 Hz. FWIW until
now no kernel-rt > 3.8 does work on my machine.
[rocketmouse@archlinux ~]$ grep HZ /mnt/debi386/boot/config-3.2.0-4-rt-686-pae
CONFIG_NO_HZ=y
# CONFIG_HZ_100 is not set
CONFIG_HZ_250=y
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=250
CONFIG_MACHZ_WDT=m
[rocketmouse@archlinux ~]$ grep CONFIG_NO_HZ_FULL /mnt/debi386/boot/config-3.2.0-4-rt-686-pae
Not available for this kernel version.
[rocketmouse@archlinux ~]$ grep HPET /mnt/debi386/boot/config-3.2.0-4-rt-686-pae
CONFIG_HPET_TIMER=y
CONFIG_HPET_EMULATE_RTC=y
CONFIG_HPET=y
CONFIG_HPET_MMAP=y
I also installed from the Debian repositories, usually I build linux-rt
myself. It IMO is a bad idea to use 250 Hz since hr timer/hpet can't be
used by everybody and for MIDI queue timer resolution you want at least
1000 Hz, assumed you care for lets say MIDI jitter.
JFTR
[rocketmouse@archlinux ~]$ grep CONFIG_NO_HZ /mnt/debi386/boot/config-3.2.0-4-rt-686-pae
CONFIG_NO_HZ=y
is not the same as CONFIG_NO_HZ_FULL.
Next time I'll test such a 250 Hz kernel, but I will install a 1000 Hz
kernel too.
Regards,
Ralf
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