Re: Linux 2.6.29-rc6

[Jesper Krogh]

john stultz wrote:
> On Wed, 2009-03-04 at 18:39 -0800, john stultz wrote:
> > On Wed, 2009-03-04 at 10:57 -0800, John Stultz wrote:
> > > On Wed, 2009-03-04 at 19:36 +0100, Jesper Krogh wrote:
> > > > jk@quad12:~$ python drift-test.py 10.192.96.19
> > > > 04 Mar 19:27:10         offset: -0.157696       drift: -693.0 ppm
> > > > 04 Mar 19:28:10         offset: -0.195134       drift: -625.098360656 ppm
> > > > 04 Mar 19:29:10         offset: -0.232579       drift: -624.595041322 ppm
> > > > 04 Mar 19:30:10         offset: -0.270021       drift: -624.408839779 ppm
> > > > 04 Mar 19:31:11         offset: -0.307461       drift: -621.727272727 ppm
> > > > 04 Mar 19:32:11         offset: -0.344903       drift: -622.185430464 ppm
> > > > 04 Mar 19:33:11         offset: -0.382345       drift: -622.491712707 ppm
> > > > 04 Mar 19:34:11         offset: -0.419794       drift: -622.727488152 ppm
> > > > 04 Mar 19:35:11         offset: -0.457239       drift: -622.89626556 ppm
> > >
> > > Yea, so from this and the settled ntpdc -c kerninfo data before, we can
> > > see that the drift is further out then the 500ppm NTP can handle.
> > >
> > > So with that at least confirmed, we can focus back on to the fast-pit
> > > tsc calibration code.
> > >
> > > Ingo, Thomas: I'm missing a bit of the context to that patch, other then
> > > just speeding up boot times, was there other rational for moving away
> > > from the ACPI PM timer based calibration?
> > >
> > > Could we maybe add a quick test that the pit reads actually take the
> > > assumed 2us max? Doing this maybe via the HPET/ACPI PM?
> > Hey Jesper,
> >
> > 	Here's a very-hackish patch to see if the approach I'm considering
> > might fix the issue you're hitting. Could you apply it, boot the kernel
> > a few times and send me the following segments of the dmesg for each of
> > those boots (the example below is from my test box)? 
> >
> > tsc delta: 44418024
> > ref_freq: 3000100  pit_freq: 3000384
> > TSC: Fast PIT calibration matches PMTIMER.
> > TSC: PIT calibration matches PMTIMER. 1 loops
> > Detected 3000.045 MHz processor.

Hi John.

Patched into 2.6.28.7 ..

First boot.
[    0.000000] tsc delta: 34203220
[    0.000000] ref_freq: 2311825  pit_freq: 2310386
[    0.000000] TSC: Fast PIT calibration matches PMTIMER.
[    0.000000] TSC: PIT calibration matches PMTIMER. 2 loops
[    0.000000] Detected 2311.877 MHz processor.
Second boot:
[    0.000000] tsc delta: 34200313
[    0.000000] ref_freq: 2311803  pit_freq: 2310190
[    0.000000] TSC: Fast PIT calibration matches PMTIMER.
[    0.000000] TSC: PIT calibration matches PMTIMER. 2 loops
[    0.000000] Detected 2311.876 MHz processor.
Third boot:
[    0.000000] tsc delta: 34198686
[    0.000000] ref_freq: 2311824  pit_freq: 2310080
[    0.000000] TSC: Fast PIT calibration matches PMTIMER.
[    0.000000] TSC: PIT calibration matches PMTIMER. 1 loops
[    0.000000] Detected 2311.872 MHz processor.
Fourth boot:
[    0.000000] tsc delta: 34199433
[    0.000000] ref_freq: 2311831  pit_freq: 2310130
[    0.000000] TSC: Fast PIT calibration matches PMTIMER.
[    0.000000] TSC: PIT calibration matches PMTIMER. 2 loops
[    0.000000] Detected 2311.821 MHz processor.



--
Jesper
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