Date: Thu, 15 Sep 2005 14:59:39 -0700 (PDT)
From: "Randy.Dunlap" <rdunlap@xenotime.net>
To: Jesper Juhl <jesper.juhl@gmail.com>
cc: linux-kernel@vger.kernel.org
Subject: Re: early printk timings way off
In-Reply-To: <200509152342.24922.jesper.juhl@gmail.com>
Message-ID: <Pine.LNX.4.58.0509151458330.1800@shark.he.net>
References: <200509152342.24922.jesper.juhl@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Thu, 15 Sep 2005, Jesper Juhl wrote:

> Early during boot the printk timings are way off :
>
> [4294667.296000] Linux version 2.6.14-rc1-git1 (juhl@dragon) (gcc version 3.3.6) #1 PREEMPT Thu Sep 15 22:25:37 CEST 2005
> [4294667.296000] BIOS-provided physical RAM map:
> [4294667.296000]  BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
> [4294667.296000]  BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
> [4294667.296000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
> [4294667.296000]  BIOS-e820: 0000000000100000 - 000000001ffec000 (usable)
> [4294667.296000]  BIOS-e820: 000000001ffec000 - 000000001ffef000 (ACPI data)
> [4294667.296000]  BIOS-e820: 000000001ffef000 - 000000001ffff000 (reserved)
> [4294667.296000]  BIOS-e820: 000000001ffff000 - 0000000020000000 (ACPI NVS)
> [4294667.296000]  BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved)
> [4294667.296000] 511MB LOWMEM available.
> [4294667.296000] On node 0 totalpages: 131052
> [4294667.296000]   DMA zone: 4096 pages, LIFO batch:1
> [4294667.296000]   Normal zone: 126956 pages, LIFO batch:31
> [4294667.296000]   HighMem zone: 0 pages, LIFO batch:1
> [4294667.296000] DMI 2.3 present.
> [4294667.296000] ACPI: RSDP (v000 ASUS                                  ) @ 0x000f69e0
> [4294667.296000] ACPI: RSDT (v001 ASUS   A7M266   0x30303031 MSFT 0x31313031) @ 0x1ffec000
> [4294667.296000] ACPI: FADT (v001 ASUS   A7M266   0x30303031 MSFT 0x31313031) @ 0x1ffec080
> [4294667.296000] ACPI: BOOT (v001 ASUS   A7M266   0x30303031 MSFT 0x31313031) @ 0x1ffec040
> [4294667.296000] ACPI: DSDT (v001   ASUS A7M266   0x00001000 MSFT 0x0100000b) @ 0x00000000
> [4294667.296000] Allocating PCI resources starting at 30000000 (gap: 20000000:dfff0000)
> [4294667.296000] Built 1 zonelists
> [4294667.296000] Kernel command line: auto BOOT_IMAGE=2.6.14-rc1-git1 ro root=801 pci=usepirqmask
> [4294667.296000] Initializing CPU#0
> [4294667.296000] CPU 0 irqstacks, hard=c03d2000 soft=c03d1000
> [4294667.296000] PID hash table entries: 2048 (order: 11, 32768 bytes)
>
> ^^^^^ These I can buy as the result of an uninitialized variable. Why are
>       we not initializing this counter to zero?
>
> [    0.000000] Detected 1400.279 MHz processor.
>
> ^^^^^ Ok, we finally seem to have initialized the counter...
>
> [   27.121583] Using tsc for high-res timesource
>
> ^^^^^ 27 seconds??? Something is off here. It certainly doesn't take 27 sec
>       to get from the previous message to this one during the actual boot.
>       What's up with that?
>
> [   27.121620] Console: colour dummy device 80x25
> [   27.122909] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
> ...
>
> No big deal, but it sure would look better (and be actually useful for the
> first few messages) if things started out at zero and then actually
> increased sanely from the very beginning.  :-)

For purposes of testing rollover and/or finding broken drivers etc.,
jiffies is init to something like -5 seconds (or max_jiffies - 5)
and then it rolls over soon.

-- 
~Randy
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