NPTL, and looking to 2.6

Matt Reppert arashi at yomerashi.yi.org
Mon Mar 3 12:44:11 PST 2003


On Mon, 03 Mar 2003 12:57:15 +0000
James Iwanek <chthon at chthon-uk.com> wrote:

> Greg Schafer wrote:
> 
> > Has anyone been keeping up with NPTL developments? I've sort of kept an
> > eye on it but haven't been game enough to try a 2.5 kernel yet. My
> > understanding (which could be totally wrong) is you need:-
> > 
> >  - 2.5 kernel headers
> >  - configure glibc with "--with-tls" for the Thread Local Storage ELF ABI
> >  - gcc-3.3 or the RHL8 branch of 3.2.x for gcc "__thread" keyword support
> > 
> > Dunno.
> > 
> > Greg
> 
> expanding on the kernel headers bit you need atleast 2.5.37 (or so the
> release notes for 0.1 say)

That's where Ingo's first threading improvements got merged ... it's my
understanding that there are other outstanding changes, like signalling
improvements, before NPTL is really useful. (This is from a quick scan
through the docs a few weeks ago, so this may not be terribly accurate ... )
Note: I'm drawing a line between "useful" and "useable". You might be able
to use NPTL to thread now, I don't know, I haven't tried (yet). But there
are things that need to happen kernel-side.

Of course, if you're not running a 2.5 kernel, you don't have the threading
improvements that make NPTL really useful and amazing :) So I'd say you'd
need to run a 2.5 kernel. (I've got a hard drive coming in, hopefully in the
next week, for my bomb box, and then I can start looking at this a little
more closely.)

As long as we're talking about changes in 2.5, since 2.6 is hopefully going
to be released in four months, people might want to familiarize themselves
with http://www.codemonkey.org.uk/post-halloween-2.5.txt which is basically
Dave Jones' list of stuff that's changed. Other than how input devices get
configured, the first thing people will probably notice is modules. Modules
got rewritten, and this started getting merged in 2.5.48. Kernels after that
WON'T WORK with the current modutils; you need to get the module-init-utils
package, which currently lives in pub/linux/kernel/people/rusty/modules
on your favorite kernel.org mirror.

(In my experience, 2.5 has been runnable since 2.5.42 or so ... that's the
first version I tried, and it works. The framebuffer is noticeably faster
than 2.4.21-pre, and I've been able to handle surprisingly large numbers
of (mostly sleeping) processes without killing the machine. If you have
a bomb box of some sort, it might be fun to try 2.5; I ran it on my desktop
without problems, but ... well, let's just say I don't want to say "try it"
and then have people come back to me an say "hey, you bastard, I lost my
system". It Worked For Me[tm].)

Matt
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