Re: [jazzplusplus-devel] Starting jackd on Mandriva

[D.B. M. <db...@ho...>]

Greets,

----------------------------------------
> Date: Tue, 20 May 2008 06:51:45 -0700
> Subject: Re: [jazzplusplus-devel] Starting jackd on Mandriva
> 
> DM = D.B. Moore
> DM>>> //my comments
> DM>>>
> DM>>> CONFIG_HZ_1000=y
> DM>>> CONFIG_HZ=1000
> DM>>>
> DM>>> //you DO have the right HZ
> DM>>>
> DM>>> # CONFIG_PREEMPT_NONE is not set
> DM>>> CONFIG_PREEMPT_VOLUNTARY=y
> DM>>> # CONFIG_PREEMPT is not set
> DM>>> # CONFIG_PREEMPT_BKL is not set
> DM>>>
> DM>>> // I haven't looked at qsynth code, but my
> DM>>> // guess is the above is the show-stopper.
> DM>>> // 'VOLUNTARY' = normal 'Desktop' preemption
> DM>>> //'Low-latency Desktop requires
> DM>>> // CONFIG_PREEMPT=y (as I do)
> DM>>>
> DM>>> CONFIG_DEFAULT_IOSCHED="cfq"
> DM>>>
> DM>>> // not actually how sure this one matters...
> DM>>> // I use DEADLINE myself as I'm more
> DM>>> // interested in linear performance
> DM>>>
> DM>>> CONFIG_TICK_ONESHOT=y
> DM>>> CONFIG_NO_HZ=y
> DM>>> CONFIG_HIGH_RES_TIMERS=y
> DM>>>
> DM>>> // I don't use the 'dynamic ticks' stuff
> DM>>> // I believe one needs the HIGH_RES_TIMER
> DM>>> // set like you have
> DM>>>
> DM>>> I believe this accounts for what you're
> DM>>> seeing with qsynth.
> 
> PS = Pete Stieber
> PS>> For the record, my Fedora x86_64 install worked OTB.
> PS>> Do you want the same information from it?
> 
> DM> Sure thing, it's a useful back-check ...and adds
> DM> to my knowledge
> 
> A gzipped version of the config file for my Fedora 8 box is attached.
> 

That has ;

CONFIG_PREEMPT_NOTIFIERS=y

in  IO-SCHEDULERS

That's not in any standard linux tree I have, might be a patch
(it'd make sense too I think, because if you've got voluntary
preemption enabled and you preempt notifications from the
io-scheduler). I was looking in the linux tree...apparently,
if 'voluntary' is selected this is where the FIFO inherits
the priority value it does. the 'low latency' option is a
different hunk of code. I imagine if you knew it were coming
you could prepare for it just before it was needed, rather
than leaving 'room' by the lowering the FIFO priority. It
would allow for raising that priority just before/as needed.

I think the AMS configure script grep's /proc/config.gz and
checks the running kernel config, and issues a warning at the
end of configure telling the user what it just found. IIRC,
it was a show-stopper until you fixed the kernel setup...

 I'll shutup about this now....but I got a few FAQ answers 
solved along the way...

Thanks for the latitude ;-).

Regards,

Donald B
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