linux-kernel - Re: TSC marked unstable on suspend and resume

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Date:	Mon, 23 Feb 2009 22:58:03 -0600
From:	David Fries <david@...es.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Ingo Molnar <mingo@...e.hu>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: TSC marked unstable on suspend and resume

On Tue, Feb 24, 2009 at 12:23:51AM +0100, Rafael J. Wysocki wrote:
> On Saturday 21 February 2009, David Fries wrote:
> > I'm getting TSC marked as unsable on hibernate to disk with
> > 2.6.29-rc3.  The last kernel I ran 2.6.24.4 ran 300+ days without a
> > problem and does not loose TSC on hibernate.
> 
> Ingo, Andrew, can you please tell us who's the right person to look into this
> problem?

I'll be looking into it, I haven't yet started debugging it.  If
anyone has a theory of operation or what I should be lookking for, I'm
all ears.  This is an old AMD K6-2 300MHz system.  I don't know if it
matters or not, but I have NO_HZ enabled, but the timer is still going
off at 1000 Hz.

I have to decide if it is worth it to split my swap partition in two
so I can hibernate both my working kernel, and the test kernel.  It
would be nice to test a kernel and pick up where I left off.  I expect
rootfstype=ext2 on the test kernel and it really will keep my
filesystem read only.

> > I'm hibernating with `echo disk > /sys/power/state`.
> > These look like the relavant messages,
> > 
> > CPU 0 irqstacks, hard=c0379000 soft=c0378000
> > PID hash table entries: 1024 (order: 10, 4096 bytes)
> > Fast TSC calibration using PIT
> > Detected 300.705 MHz processor.
> > Calibrating delay loop (skipped), value calculated using timer frequency.. 601.41 BogoMIPS (lpj=300705)
> > hibernate to disk,
> > Restarting tasks ... done.
> > Clocksource tsc unstable (delta = 499883531 ns)
> > 
> > another reboot,
> > Restarting tasks ... done.
> > Clocksource tsc unstable (delta = 499883531 ns)
> > 
> > another reboot,
> > Freezing user space processes ... (elapsed 0.07 seconds) done.
> > Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done.
> > PM: Shrinking memory...  ^H-<4>Clocksource tsc unstable (delta = 78961880 ns)
> > ^H\^H|^H/^Hdone (34745 pages freed)
> > 
> > 
> > 
> > I didn't spot the problem until I raw the HP48 calculator emulator x48
> > and it was running like a dog, but the same binary ran fine on my
> > other systems.  It was looping on gettimeofday intending to delay 2us,
> > but was getting 1ms when TSC wasn't available.
> > 
> > On Thu, Feb 05, 2009 at 10:02:39PM +0100, Ingo Molnar wrote:
> > > What does this tool output:
> > > 
> > >  http://people.redhat.com/mingo/time-warp-test/time-warp-test.c
> > 
> > time-warp-test is getting the number of CPUs wrong here, trivial
> > patch included.
> > 
> > ./time-warp-test  
> > 2 CPUs, running 2 parallel test-tasks.
> > 
> > grep processor /proc/cpuinfo
> > processor       : 0
> > model name      : AMD-K6(tm) 3D processor
> > 
> > 
> > --- time-warp-test.c.orig	2009-02-19 20:52:40.000000000 -0600
> > +++ time-warp-test.c	2009-02-19 21:32:58.000000000 -0600
> > @@ -295,7 +295,7 @@ int main(int argc, char **argv)
> >  	unsigned long *shared;
> >  	unsigned long cpus, tasks;
> >  
> > -	cpus = system("exit `grep processor /proc/cpuinfo  | wc -l`");
> > +	cpus = system("exit `grep ^processor /proc/cpuinfo  | wc -l`");
> >  	cpus = WEXITSTATUS(cpus);
> >  
> >  	if (argc > 2) {
> > 
> > 
> > 
> > 
> > With any optimizations, -O or -O1 or -O2 I don't get any status
> > output, with -O0 I get,
> > 
> > ./time-warp-test 
> > 1 CPUs, running 1 parallel test-tasks.
> > checking for time-warps via:
> > - read time stamp counter (RDTSC) instruction (cycle resolution)
> > 
> >  | TSC: 0.82us, fail:0 /
> --
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-- 
David Fries <david@...es.net>
http://fries.net/~david/ (PGP encryption key available)
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