linux-kernel - Re: v2.6.21.5-rt19

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Message-Id: <1183758545.20747.34.camel@cmn3.stanford.edu>
Date:	Fri, 06 Jul 2007 14:49:04 -0700
From:	Fernando Lopez-Lezcano <nando@...ma.Stanford.EDU>
To:	Rui Nuno Capela <rncbc@...bc.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	RT-Users <linux-rt-users@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	"jcaceres@...ma.Stanford.EDU" <jcaceres@...ma.Stanford.EDU>,
	Carsten Emde <carsten.emde@...dl.org>
Subject: Re: v2.6.21.5-rt19

On Fri, 2007-07-06 at 15:10 +0100, Rui Nuno Capela wrote:
> Hi,
> 
> On Wed, July 4, 2007 21:49, Thomas Gleixner wrote:
> > I'm pleased to announce the v2.6.21.5-rt19 kernel on behalf of Ingo.
> >
> >
> > It can be downloaded from the usual place:
> >
> > http://people.redhat.com/mingo/realtime-preempt/
> >
> > More info about the -rt patch set can be found in the RT wiki:
> >
> > http://rt.wiki.kernel.org
> >
> > Changes since 2.6.21.5-rt18:
> >
> > - Fixed a nasty and hard to track down slowness / boot problem on SMP
> > machines with CONFIG_NOHZ enabled. The problem was caused by the timer
> > wheel base lock held during the get_next_timer_interrupt() call in the
> > idle path, which eventually led to a bogus PI boosting of the idle task
> > and in consequence a stale wrong scheduler selection for the affected idle
> > task.
> >
> > Kudos to Carsten Emde, who patiently and meticulously isolated the
> > problem and provided the traces, which allowed to identify the root cause.
> >
> > Problem solution: Prevent idle task boosting
> >
> > - back port of the ntp / clock_was_set fix
> >
> > - integration of the processor_idle fix from Venki Pallipadi, which
> > resolves boot issues on some platforms
> >
> > - ep93xx clock events fix from Manfred Gruber
> >
> 
> Maybe someone remember me whining about troubles with 2.6.21-rt2..18 on my
> Core2 T7200 laptop (fujitsu-siemens amilo i1520).
> 
> Althought I'm still with my fingers crossed, I can tell the good news are
> that 2.6.21.5-rt19 (and -rt20) does behave far better now on the very same
> box.

Yes, it works much better indeed...

Ingo: is there a place where I can read about the changes in different
rtxx releases? What is new/better/fixed in rt20? (I see scheduler stuff
in a diff from rt19 to rt20 but I don't really know what it means). 

-- Fernando

> I've more than 8 hours up and running now, without a single glimpse of the
> bad symptoms, which used to show in a matter of minutes if not earlier
> during init time.
> 
> Congratulations. I'm not sure whether this problem can be closed for good,
> though, just because you mention the slowness fix applies to CONFIG_NOHZ=Y
> and I'm quite sure my badness surged either way.
> 
> But at least -rt is usable again here and that just makes me happier :)
> 
> Cheers.


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