Re: [LAU] More recent kernel config options

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
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Received on Mon Jul 27 08:15:03 2009