linux-kernel - Re: [2.6.28-rc5] TSC sync error and high hrtimer_start (was: Bootup time regression from 2.6.27 to 2.6.28-rc3+)

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Message-Id: <200811170318.23640.elendil@planet.nl>
Date:	Mon, 17 Nov 2008 03:18:22 +0100
From:	Frans Pop <elendil@...net.nl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Lukas Hejtmanek <xhejtman@....muni.cz>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	corsac@...ian.org
Subject: Re: [2.6.28-rc5] TSC sync error and high hrtimer_start (was: Bootup time regression from 2.6.27 to 2.6.28-rc3+)

On Sunday 16 November 2008, Frans Pop wrote:
> Possibly this may be related to this diff in the boot messages:
> -checking TSC synchronization [CPU#0 -> CPU#1]: passed.
> +checking TSC synchronization [CPU#0 -> CPU#1]:
> +Measured 696 cycles TSC warp between CPUs, turning off TSC clock.
> +Marking TSC unstable due to check_tsc_sync_source failed
>
> With .27.4 TSC _always_ passed. Now, with .28-rc5 I get this warp. I've
> done two boots so far, for the other one the warp was 680 cycles.

Maybe this extra context a bit earlier in dmesg is relevant here:

-Calibrating delay loop (skipped), value calculated using timer frequency.. 6399.76 BogoMIPS (lpj=12799520)
+HPET: 3 timers in total, 0 timers will be used for per-cpu timer
+Calibrating delay loop (skipped), value calculated using timer frequency.. 6399.73 BogoMIPS (lpj=12799476)
[...]
-ACPI: Core revision 20080609
+ACPI: Core revision 20080926
+Setting APIC routing to flat
 ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
 CPU0: Intel(R) Pentium(R) D CPU 3.20GHz stepping 07
-Using local APIC timer interrupts.
-APIC timer calibration result 12499520
-Detected 12.499 MHz APIC timer.
-Booting processor 1/1 ip 6000
+Booting processor 1 APIC 0x1 ip 0x6000
 Initializing CPU#1
-Calibrating delay using timer specific routine.. 6399.94 BogoMIPS (lpj=12799898)
+Calibrating delay using timer specific routine.. 6198.05 BogoMIPS (lpj=12396107)

Note the rather large difference in BogoMIPS between core 0 and 1.
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