21 Jul
2007
21 Jul
'07
9:40 p.m.
On Saturday 21 July 2007, Atte André Jensen wrote:
The lowlatency kernel of ubuntu is not a realtime kernel. And for your home
made kernel, please let us see your .config
e.g.
~$ grep PREEMPT /boot/config-$(uname -r)
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT_DESKTOP is not set
CONFIG_PREEMPT_RT=y
^^^^^^^^^^^^^^^
CONFIG_PREEMPT=y
CONFIG_PREEMPT_SOFTIRQS=y
CONFIG_PREEMPT_HARDIRQS=y
CONFIG_PREEMPT_BKL=y
CONFIG_PREEMPT_RCU=y
# CONFIG_DEBUG_PREEMPT is not set
# CONFIG_CRITICAL_PREEMPT_TIMING is not set
I underlined the relevant line there
--
Palimm Palimm!
http://tapas.affenbande.org
Which kernel
version is this?
Homemade (with mingo rt-patch) 2.6.18-rt7
2.6.20-16-lowlatency On Debian, I get ksoftirqd as well, one
per processor core. ksoftirqd is part of the 2.6 kernel series. I
imagine you're still using a 2.4 kernel on your Debian system,
Nope...
or the
kernel is configured and built differently to mine.
Might be...
It may be possible to rebuild the Ubuntu kernel
you are using to match
what you are used to, but I don't know if that will get you what you
want.
I grabbed a vanilla 2.6.22.1 and applied the latest patch and quick
testing seems to suggest that the system is running at least at well as
under debian:
atte@ajstrup:~$ uname -r
2.6.22.1-rt4
atte@ajstrup:~$ ps aux | grep IRQ
root 36 0.0 0.0 0 0 ? S< 18:15 0:00 [IRQ-9]
root 268 0.0 0.0 0 0 ? S< 18:16 0:00 [IRQ-4]
root 292 0.0 0.0 0 0 ? S< 18:16 0:00
[IRQ-12]
root 293 0.0 0.0 0 0 ? S< 18:16 0:00 [IRQ-1]
root 1108 0.0 0.0 0 0 ? S< 18:16 0:00
[IRQ-14]
root 1139 0.0 0.0 0 0 ? S< 18:16 0:00
[IRQ-15]
root 1140 0.2 0.0 0 0 ? S< 18:16 0:02
[IRQ-11]
root 1936 0.0 0.0 0 0 ? S< 18:16 0:00 [IRQ-8]
root 2025 0.0 0.0 0 0 ? S< 18:16 0:00 [IRQ-7]
root 2103 0.3 0.0 0 0 ? S< 18:16 0:03
[IRQ-10]
root 3432 0.0 0.0 0 0 ? S< 18:16 0:00 [IRQ-3]
atte 4674 0.0 0.0 2888 772 pts/2 R+ 18:33 0:00 grep
IRQ
I've never tried setting real-time priority
on kernel threads
like that, and I don't know if it would achieve anything. I trust it
did for you?
Alot!
Bottom line: It seems it's still necessary to roll your own kernel to
get optimal realtime performance under ubuntu :-(