[LAU] More recent kernel config options

[William Weston]

On Sun, 26 Jul 2009, Brent Busby wrote:
> On Sun, 26 Jul 2009, Ken Restivo wrote:
>
>>> I've also run into a handful of config options that either help or hurt
>>> realtime performance, depending on the specific hardware:
>>> 
>>> NO_HZ (seems to work properly on most hardware these days)
>> 
>> Is that advised? I was told to use HZ_1000 in order to get MIDI to work 
>> correctly. Should I be using NO_HZ instead? I've got several machines to 
>> configure: a 32-bit Atom EEE, a 64-bit Intel Micro-ITX, and a 64-bit Asus 
>> Intel Core2Duo
>
> Oddly (and I don't really understand this), you can have *both*.  I've seen 
> recommendations online from people who claim to have gotten good results with 
> Jack even on laptops by having NO_HZ and HZ_1000 selected. I don't really 
> know what the effect of this is.  Does this mean you generate no ticks except 
> when you need them, but when you do, the jiffy rate is 1000Hz?  This naively 
> seems to me like a better idea than just running a clock all the time, but I 
> don't know how that pans out for recording and MIDI.

Ahh.  This explains why I've had good results with NO_HZ for the 
last year.  I have both NO_HZ and HZ_1000 enabled.  I still don't 
understand how these two interact.  At the very least, this would 
provide the fallback for booting the kernel with nohz=off.

> It seems like there ought to be more pooling of resources regarding complete 
> kernel configs that work.  Everyone always talks about the patches 
> themselves...but anyone who can do 'patch -p1' against a tree of source code 
> can get that part right.
>
> -- 
> + Brent A. Busby	 + "We've all heard that a million monkeys
> + UNIX Systems Admin	 +  banging on a million typewriters will
> + University of Chicago	 +  eventually reproduce the entire works of
> + Physical Sciences Div. +  Shakespeare.  Now, thanks to the Internet,
> + James Franck Institute +  we know this is not true." -Robert Wilensky

I'm willing to post my config for the AMD laptop once I get the 
right combination of HZ, RTC, and HPET options set.  I'm still 
running Fedora 8 on my Core2Quad, so I've stopped at 2.6.24.7-rt27 
with everything running perfectly, but I can post the config from 
that box if anyone is interested.

Cheers,
--ww