linux-kernel - Re: [Bug #12064] [regression] Measured 688 cycles TSC warp; marking TSC unstable

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Message-ID: <20081123163240.GA5884@elte.hu>
Date:	Sun, 23 Nov 2008 17:32:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frans Pop <elendil@...net.nl>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Bug #12064] [regression] Measured 688 cycles TSC warp;
	marking TSC unstable


* Frans Pop <elendil@...net.nl> wrote:

> On Saturday 22 November 2008, Rafael J. Wysocki wrote:
> > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=12064
> > Date		: 2008-11-16 19:27:43 (7 days old)
> > References	: http://marc.info/?l=linux-kernel&m=122686370308852&w=2
> 
> Looks to be fixed in -rc6:
> 
> -Calibrating delay using timer specific routine.. 6198.05 BogoMIPS (lpj=12396107)
> +Calibrating delay using timer specific routine.. 6399.82 BogoMIPS (lpj=12799647)
> [...]
> -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
> +checking TSC synchronization [CPU#0 -> CPU#1]: passed.
> 
> So, BogoMIPS value on CPU#1 is in line with CPU#0 again and TSC passes.
> No idea what commit would be responsible.

this one from Venki fixed it:

| commit 93ce99e849433ede4ce8b410b749dc0cad1100b2
| Author: Venki Pallipadi <venkatesh.pallipadi@...el.com>
| Date:   Mon Nov 17 14:43:58 2008 -0800
| 
|    x86: add rdtsc barrier to TSC sync check

	Ingo
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