linux-kernel - Re: [git pull] scheduler changes for v2.6.26

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Date:	Wed, 23 Apr 2008 10:11:43 +0200
From:	Mike Galbraith <efault@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frans Pop <elendil@...net.nl>, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Richard Jonsson <richie@...erworld.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [git pull] scheduler changes for v2.6.26


On Tue, 2008-04-22 at 14:25 +0200, Mike Galbraith wrote:
> On Tue, 2008-04-22 at 10:59 +0200, Ingo Molnar wrote:
> > * Mike Galbraith <efault@....de> wrote:
> > 
> > > > the 700-800 msecs of delays you see are very "brutal" so there must 
> > > > be something fundamentally wrong going on here.
> > > 
> > > I'm seeing latency hits with 26.git, whereas 25 is hit free.
> > 
> > ok. I think what happens is that your broken sched-clock hid the real 
> > breakage. Lets try fix the real breakage now.
> > 
> > I've uploaded a new sched-devel.git that is against very latest -git, 
> > could you try ftrace (with a sufficiently large 
> > /debug/tracing/tracing_max_entries value) - perhaps the 
> > worst-case-wakeup-latency tracer shows large latencies? If not, then 
> > maybe the sched_switch tracer gives a better insight into what's 
> > happening?
> 
> Well, looks like this is going to have to wait.  sched-devel is locking
> hard on me, both sched-devel and .git are losing my darn keyboard right
> in the middle of things, and my serial ports are (still) so screwed up I
> can't get minicom working right.  Arg.

I dug my old p3/500 out and hooked it up since I still can't get minicom
functional plugging P4->Q6600, but no joy.  Whatever the heck is going
wrong in sched-devel is so catastrophic that not one character hits the
console when it locks, and nmi_watchdog=1 does nada.

FWIW, all I am doing is listening to music in amarok while a make -j4
glibc build is running, watching latencytop and watch-rq-clock.sh (nice
-15).  Latency hits are smaller, but still present without NO_HZ btw.
The largest I ever saw in latencytop before death arrived was < 300ms.
(still size mondo)

config attached.

	-Mike

Download attachment "config.gz" of type "application/x-gzip" (16694 bytes)