Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from 2.6.24)

Gabriel C
2008-05-08T12:22:20Z

Thomas Gleixner wrote:
> On Wed, 7 May 2008, Martin Knoblauch wrote:
>>> no this looks different. As soon as the timesource is detected, I see non-zero
>>> timestamps
>>> in dmesg, but they look smaller and jump in both directions. And I have never
>>> seen this before
>>> 2.6.25.
>>>
>>> It actually might be a good idea to get the dmesg output from 2.6.24.
>>>
>>> Cheers
>>> Martin
>> interesting - maybe related to clocksources. The HPET seems to be detected later in 2.6.25:
>>
>> 2.6.24:
>>
>> [ 0.000000] Initializing CPU#0
>> [ 0.000000] PID hash table entries: 4096 (order: 12, 32768 bytes)
>> -->[ 0.000000] hpet clockevent registered
>> -->[ 0.000000] TSC calibrated against HPET
>
>> 2.6.25.2:
>>
>> [ 0.000000] Initializing CPU#0
>> [ 0.000000] PID hash table entries: 4096 (order: 12, 32768 bytes)
>> -->[ 0.000000] TSC calibrated against PM_TIMER
>
> That's odd indeed. Is HPET not registered at all in 2.6.25 or does it just happen late ?
>
> please provide the output of:
> /sys/devices/system/clocksource/clocksource0/available_clocksource
> /sys/devices/system/clocksource/clocksource0/current_clocksource

I was about to report / ask bout this issue too.

I see the same output for >=2.6.25 , TSC calibrated against PM_TIMER and not against HPET anymore.

[ 0.000000] TSC calibrated against PM_TIMER
[ 0.000016] time.c: Detected 2499.949 MHz processor.
...
[ 0.000999] hpet clockevent registered

So it seems to register to late in >=2.6.25 kernels ?

cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc hpet acpi_pm jiffies

cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc

>
> Thanks,
> tglx

Regards,

Gabriel C