[LAD] 2.4 vs 2.6

[pete shorthose]

On Sat, 2007-07-21 at 22:53 -0400, . wrote:
> > > > wrote:
> > > > > I've been working with the 2.6 series kernel now for some
> > time with satisfactory
> 
> > when
> > you all say RT Patched you mean realtime module built, loaded configured and
> > used by jack correct?
> 
> please learn how to quote. heres a screenshot: http://whats-your.name/i/bloglines_blows.png
> 
> bloglines really should stick to the blogosphere instead of mucking with mailing lists..

it's word wrap doing the most damage there.

> realtime isnt a module, its a big kernel patch.

no. "realtime" is a condition. RT patched refers to ingo
molnars realtime preempt patches. 
( http://people.redhat.com/mingo/realtime-preempt/ )
that people refer to all kinds of things as "realtime" just
makes it harder to figure out what they are referring to
without some specific context.

confusingly, the realtime lsm *module* is basically a tool
for assigning the correct permissions to your apps. 
(lsm stands for linux security module)
it's also redundant in the face of rlimits which is another
method of doing the same thing but one that is included
in the mainstream kernel. 

more confusingly still, rlimits can be configured by
different methods too. via a supporting PAM 
(/etc/security/limits.conf) or by set_rtlimits which is a
command line tool with it's own configuration file.

even more confusingly, you may not need to patch your
kernel at all for several reasons.

1. over time elements of the rt patches have been
 merged into the mainline kernel.

2. some distros feature prebuilt low latency kernels

3. some distros are dedicated to audio and are built from the
   ground up with respect to low latency issues.

i'd advise those not familiar with the details to avoid building
a kernel unless they've tried what's available in their own distro
first, and found it lacking. 

anyway check out these two links for some background:

"Realtime Preemption"
http://tapas.affenbande.org/wordpress/?page_id=6

"Linux Audio/MIDI Realtime System Setup"
http://tapas.affenbande.org/wordpress/?page_id=73

i'm not sure if these pages are kept rigidly up to
date but they are great for getting a handle on
the issues. hats off to tapas (Florian Schmidt)
 
>  my experience (not on ia32) is that it usually either 1)
>  doesnt compile 2) doesnt boot 3) freezes up some 
> time during the boot sequence 4) freezes up some time
> afterwards. i havent tried mingo since about 2.6.18 though
>  so maybe theres been a night and day change.. 

i think they manage quite well over at 64studio.
http://64studio.com/faq_developer

> vanilla is fine, except for the lack of reiser4, which you dont want to use for audio anyways

indeed. well, perhaps you too should stick to blogs 
where overheated, unproductive and self indulgent
diatribes are the norm. here, you risk being the exception.

pete.