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

Martin Knoblauch
2008-05-07T15:50:40Z

> From: Martin Knoblauch <spamtrap@knobisoft.de>
> To: Bart Van Assche <bart.vanassche@gmail.com>
> Cc: linux-kernel@vger.kernel.org; hmh@hmh.eng.br
> Sent: Wednesday, May 7, 2008 5:02:23 PM
> Subject: Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from 2.6.24)
>
> ----- Original Message ----
>
> > From: Bart Van Assche
> > To: Martin Knoblauch
> > Cc: linux-kernel@vger.kernel.org; hmh@hmh.eng.br
> > Sent: Wednesday, May 7, 2008 3:06:02 PM
> > Subject: Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from
> 2.6.24)
> >
> > On Wed, May 7, 2008 at 2:42 PM, Martin Knoblauch wrote:
> > >
> > > any news on the one below? I upgraded to 2.6.25.2 and the problem still
> > persists. Would adding a bugzilla actually help ? :-)
> > >
> > > http://www.ussg.iu.edu/hypermail/linux/kernel/0804.2/1144.html
> >
> > I noticed a similar issue on 2.6.22 and 2.6.24 kernels: with ACPI
> > disabled Linux' clock jumps backward and forward early during boot.
> > See also the kernel messages from the attachment in comment #13 of
> > http://bugzilla.kernel.org/show_bug.cgi?id=9936.
> >
> > Bart,
>
> Hi Bart,
>
> 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
[ 150.233392] time.c: Detected 2327.502 MHz processor.
[ 150.235525] Console: colour VGA+ 80x25
[ 150.235532] console [tty0] enabled
[ 150.235546] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[ 150.235548] ... MAX_LOCKDEP_SUBCLASSES: 8
[ 150.235549] ... MAX_LOCK_DEPTH: 30
[ 150.235550] ... MAX_LOCKDEP_KEYS: 2048
[ 150.235551] ... CLASSHASH_SIZE: 1024
[ 150.235552] ... MAX_LOCKDEP_ENTRIES: 8192
[ 150.235553] ... MAX_LOCKDEP_CHAINS: 16384
[ 150.235554] ... CHAINHASH_SIZE: 8192
[ 150.235556] memory used by lock dependency info: 1712 kB
[ 150.235557] per task-struct memory footprint: 2160 bytes
[ 150.235559] Checking aperture...
[ 150.235568] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[ 150.267666] Placing software IO TLB between 0x123c000 - 0x523c000
[ 150.377395] Memory: 8086092k/9437184k available (2901k kernel code, 301896k reserved, 1534k data, 772k init)
[ 150.454897] Calibrating delay using timer specific routine.. 4659.71 BogoMIPS (lpj=9319423)

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
[ 0.000004] time.c: Detected 2327.497 MHz processor.
[ 0.002079] Console: colour VGA+ 80x25
[ 0.002086] console [tty0] enabled
[ 0.002107] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[ 0.002109] ... MAX_LOCKDEP_SUBCLASSES: 8
[ 0.002110] ... MAX_LOCK_DEPTH: 48
[ 0.002111] ... MAX_LOCKDEP_KEYS: 2048
[ 0.002112] ... CLASSHASH_SIZE: 1024
[ 0.002114] ... MAX_LOCKDEP_ENTRIES: 8192
[ 0.002115] ... MAX_LOCKDEP_CHAINS: 16384
[ 0.002116] ... CHAINHASH_SIZE: 8192
[ 0.002117] memory used by lock dependency info: 1712 kB
[ 0.002119] per task-struct memory footprint: 3456 bytes
[ 0.002121] Checking aperture...
[ 0.002130] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[ 0.004000] Placing software IO TLB between 0x15093000 - 0x19093000
[ 0.004000] Memory: 8110236k/9437184k available (2950k kernel code, 277752k reserved, 1567k data, 800k init)
[ 0.004000] CPA: page pool initialized 1 of 1 pages preallocated
-->[ 0.004000] hpet clockevent registered
[ 0.080008] Calibrating delay using timer specific routine.. 4660.31 BogoMIPS (lpj=9320632)

Any ideas how to force hpet earlier? Specifying hpet=force and/or clocksource=hpet did not help.

Cheers
Martin