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SubjectRe: Clock jumps
On 28.05.2010 02:00, john stultz wrote:

Hi John,

> Looking at the diff:
> --- dmesg-lenny 2010-05-27 16:45:33.000000000 -0700
> +++ dmesg-squeeze 2010-05-27 16:46:14.000000000 -0700
> @@ -132,8 +132,8 @@
> console [ttyS1] enabled
> hpet clockevent registered
> Fast TSC calibration using PIT
> -Detected 2660.398 MHz processor.
> -Calibrating delay loop (skipped), value calculated using timer frequency.. 5320.79 BogoMIPS (lpj=10641592)
> +Detected 2613.324 MHz processor.
> +Calibrating delay loop (skipped), value calculated using timer frequency.. 5226.64 BogoMIPS (lpj=10453296)
> Security Framework initialized
> Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
> Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
> @@ -160,7 +160,7 @@
> CPU0: Intel(R) Xeon(R) CPU 3075 @ 2.66GHz stepping 0b
> Booting Node 0, Processors #1
> Brought up 2 CPUs
> -Total of 2 processors activated (10640.79 BogoMIPS).
> +Total of 2 processors activated (10546.63 BogoMIPS).
> NET: Registered protocol family 16
> ACPI: bus type pci registered
> PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0xe0000000-0xefffffff] (base 0xe0000000)
>
> So you can see in the above the during the second boot the TSC
> calibration was badly mis-calculated. This was the cause of the skew.
>
> Not sure how that might be linked to the distro upgrade. It could have
> been something like SMI damage during the calibration time, but I
> thought the calibration loop watched for that.
>
> Bernhard: I expect with all those vms, this machine isn't rebooted
> frequently. So could you look at the logs to see how much the "Detected
> xxxx.yyy MHz processor." line varies by across a few other boots (if
> they still exist?).

Correct, the box isn't rebooted often, but I do have a few dmesg outputs
laying around. lpj was always almost the same until the very last boot
which screwed up the clock.

dmesg:[ 0.000000] Linux version 2.6.33 (root@svr02) (gcc version
4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Sun Mar 7 23:01:45 CET 2010
dmesg:[ 0.008005] Calibrating delay loop (skipped), value calculated
using timer frequency.. 5226.64 BogoMIPS (lpj=10453296)
dmesg:[ 0.288002] Total of 2 processors activated (10546.63 BogoMIPS).
dmesg.0:[ 0.000000] Linux version 2.6.33 (root@svr02) (gcc version
4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Sun Mar 7 23:01:45 CET 2010
dmesg.0:[ 0.008005] Calibrating delay loop (skipped), value
calculated using timer frequency.. 5320.79 BogoMIPS (lpj=10641592)
dmesg.0:[ 0.274022] Total of 2 processors activated (10640.79 BogoMIPS).
dmesg.1.gz:[ 0.000000] Linux version 2.6.32-rc7 (root@svr02) (gcc
version 4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Thu Nov 19 14:36:03 CET 2009
dmesg.1.gz:[ 0.012004] Calibrating delay loop (skipped), value
calculated using timer frequency.. 5319.06 BogoMIPS (lpj=10638120)
dmesg.1.gz:[ 0.016000] Calibrating delay using timer specific
routine.. 5319.99 BogoMIPS (lpj=10639980)
dmesg.1.gz:[ 0.260003] Total of 2 processors activated (10639.05
BogoMIPS).
dmesg.2.gz:[ 0.000000] Linux version 2.6.32-rc7 (root@svr02) (gcc
version 4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Thu Nov 19 14:36:03 CET 2009
dmesg.2.gz:[ 0.012005] Calibrating delay loop (skipped), value
calculated using timer frequency.. 5319.35 BogoMIPS (lpj=10638712)
dmesg.2.gz:[ 0.016000] Calibrating delay using timer specific
routine.. 5319.99 BogoMIPS (lpj=10639990)
dmesg.2.gz:[ 0.261567] Total of 2 processors activated (10639.35
BogoMIPS).
dmesg.3.gz:[ 0.000000] Linux version 2.6.32-rc7 (root@svr02) (gcc
version 4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Thu Nov 19 14:36:03 CET 2009
dmesg.3.gz:[ 0.012005] Calibrating delay loop (skipped), value
calculated using timer frequency.. 5319.97 BogoMIPS (lpj=10639956)
dmesg.3.gz:[ 0.016000] Calibrating delay using timer specific
routine.. 5319.99 BogoMIPS (lpj=10639987)
dmesg.3.gz:[ 0.257152] Total of 2 processors activated (10639.97
BogoMIPS).
dmesg.4.gz:[ 0.000000] Linux version 2.6.32-rc7 (root@svr02) (gcc
version 4.3.2 (Debian 4.3.2-1.1) ) #1 SMP Thu Nov 19 14:36:03 CET 2009
dmesg.4.gz:[ 0.012005] Calibrating delay loop (skipped), value
calculated using timer frequency.. 5319.84 BogoMIPS (lpj=10639688)
dmesg.4.gz:[ 0.016000] Calibrating delay using timer specific
routine.. 5319.99 BogoMIPS (lpj=10639993)
dmesg.4.gz:[ 0.253571] Total of 2 processors activated (10639.84
BogoMIPS).

If necessary I can reboot once more, but I'd like to avoid it.

Bernhard


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