linux-kernel - Re: CONFIG_PRINTK_TIME broken on git HEAD ?

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Date:	Thu, 08 May 2008 13:13:58 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Gabriel C <nix.or.die@...glemail.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: CONFIG_PRINTK_TIME broken on git HEAD ?

On Thu, 2008-05-08 at 13:00 +0200, Gabriel C wrote:

> >>From my log 2.6.26-rc1-00065-g5717922 was fine.
> > 
>  
> > May  6 00:13:14 thor kernel: [    0.000000] Allocating PCI resources starting at d0000000 (gap: cf600000:2f800000)
> > May  6 00:13:14 thor kernel: [    0.000000] SMP: Allowing 4 CPUs, 0 hotplug CPUs
> > May  6 00:13:14 thor kernel: [    0.000000] PERCPU: Allocating 41732 bytes of per cpu data
> > May  6 00:13:14 thor kernel: [    0.000000] Kernel command line: root=/dev/sdb1 ro debug vga=0x317
> > May  6 00:13:14 thor kernel: [    0.000000] Preemptible RCU implementation.
> > May  6 00:13:14 thor kernel: [    0.000000] Extended CMOS year: 2000
> > May  6 00:13:14 thor kernel: [    0.000000] TSC calibrated against PM_TIMER
> > May  6 00:13:14 thor kernel: [    0.000014] time.c: Detected 2499.952 MHz processor.
> > May  6 00:13:14 thor kernel: [    0.000032] console [tty0] enabled
> > May  6 00:13:14 thor kernel: [    0.000999] Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
> > May  6 00:13:14 thor kernel: [    0.000999] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
> > May  6 00:13:14 thor kernel: [    0.000999] Checking aperture...
> > 
> > ...
> > 
> >>> dmesg shows here :
> >>>
> >>> ...
> >>>
> >>>
> >>> [    0.000000] Allocating PCI resources starting at d0000000 (gap: cf600000:2f800000)
> >>> [    0.000000] SMP: Allowing 4 CPUs, 0 hotplug CPUs
> >>> [    0.000000] PERCPU: Allocating 42756 bytes of per cpu data
> >>> [    0.000000] NR_CPUS: 8, nr_cpu_ids: 4
> >>> [4294014.506571] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 1010753
> >>> [4294014.506571] Kernel command line: root=/dev/sdb1 ro debug vga=0x317
> >>> [4294014.506571] Initializing CPU#0
> >>> [4294014.506571] Preemptible RCU implementation.
> >>> [4294014.506571] PID hash table entries: 4096 (order: 12, 32768 bytes) 


> I've bisected it.

> cat ./.git/refs/bisect/bad
> 3e51f33fcc7f55e6df25d15b55ed10c8b4da84cd
> 
>  git show 3e51f33fcc7f55e6df25d15b55ed10c8b4da84cd
>  commit 3e51f33fcc7f55e6df25d15b55ed10c8b4da84cd
>  Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>  Date:   Sat May 3 18:29:28 2008 +0200
>  
>      sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
>  
>      this replaces the rq->clock stuff (and possibly cpu_clock()).
>  
>       - architectures that have an 'imperfect' hardware clock can set
>         CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
>  
>       - the 'jiffie' window might be superfulous when we update tick_gtod
>         before the __update_sched_clock() call in sched_clock_tick()
>  
>       - cpu_clock() might be implemented as:
>  
>           sched_clock_cpu(smp_processor_id())
>  
>         if the accuracy proves good enough - how far can TSC drift in a
>         single jiffie when considering the filtering and idle hooks?
>  
>      [ mingo@...e.hu: various fixes and cleanups ]
>  
>      Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>      Signed-off-by: Ingo Molnar <mingo@...e.hu>
>                                                                                                                                                              

Ok, so the issue is that the clock doesn't start at 0, but at:
4294014.506571 ?

I guess that's a side-effect of using ktime to base the clock off.
Thomas, do we have a clock that is uptime based?


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