linux-kernel - Re: [PATCH 13/15] sched: Use a static_key for sched_clock

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Message-ID: <20140122120048.GB389@x4>
Date:	Wed, 22 Jan 2014 13:00:48 +0100
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Arjan van de Ven <arjan@...ux.intel.com>, lenb@...nel.org,
	rjw@...ysocki.net, Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	rui.zhang@...el.com, jacob.jun.pan@...ux.intel.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>, hpa@...or.com,
	paulmck@...ux.vnet.ibm.com, Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Andy Lutomirski <luto@...capital.net>,
	linux-kernel@...r.kernel.org, dyoung@...hat.com
Subject: Re: [PATCH 13/15] sched: Use a static_key for sched_clock_stable

On 2014.01.22 at 11:45 +0100, Peter Zijlstra wrote:
> On Tue, Jan 21, 2014 at 05:28:37PM -0500, Sasha Levin wrote:
> > On 12/12/2013 09:08 AM, Peter Zijlstra wrote:
> > 
> > This patch seems to be causing an issue with booting a KVM guest. It seems that it
> > causes the time to go random during early boot process:
> > 
> > 	[    0.000000] Initmem setup node 30 [mem 0x12ee000000-0x138dffffff]
> > 	[    0.000000]   NODE_DATA [mem 0xcfa42000-0xcfa72fff]
> > 	[    0.000000]     NODE_DATA(30) on node 1
> > 	[    0.000000] Initmem setup node 31 [mem 0x138e000000-0x142fffffff]
> > 	[    0.000000]   NODE_DATA [mem 0xcfa11000-0xcfa41fff]
> > 	[    0.000000]     NODE_DATA(31) on node 1
> > 	[    0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00
> > 	[    0.000000] kvm-clock: cpu 0, msr 0:cf991001, boot clock
> > 	[133538.294040] Zone ranges:
> > 	[133538.294338]   DMA      [mem 0x00001000-0x00ffffff]
> > 	[133538.294804]   DMA32    [mem 0x01000000-0xffffffff]
> > 	[133538.295223]   Normal   [mem 0x100000000-0x142fffffff]
> > 	[133538.295670] Movable zone start for each node
> > 

FYI it happens on real hardware on my machine:
...
[    0.000000] Hierarchical RCU implementation.
[    0.000000] NR_IRQS:4352 nr_irqs:712 16
[    0.000000] spurious 8259A interrupt: IRQ7.
[    0.000000] Console: colour VGA+ 80x25
[    0.000000] console [tty0] enabled
[    0.000000] hpet clockevent registered
[    0.000000] tsc: Fast TSC calibration using PIT
[    0.003333] tsc: Detected 3210.681 MHz processor
[   60.375238] Calibrating delay loop (skipped), value calculated using timer frequency.. 6423.91 BogoMIPS (lpj=10702270)
[   60.375240] pid_max: default: 32768 minimum: 301
[   60.375259] Mount-cache hash table entries: 256
[   60.375373] tseg: 0000000000
[   60.375377] CPU: Physical Processor ID: 0
[   60.375377] CPU: Processor Core ID: 0
[   60.375378] mce: CPU supports 6 MCE banks
[   60.375382] LVT offset 0 assigned for vector 0xf9
[   60.375384] process: using AMD E400 aware idle routine
[   60.375386] Last level iTLB entries: 4KB 512, 2MB 16, 4MB 8
...
-- 
Markus
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