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SubjectRe: kernel panic on NHM EX machine
On 04/12/2012 10:46 AM, Fengguang Wu wrote:

> Hi all,
>
> This commit makes a difference. Found by auto bisection and confirmed
> by reverting it on top of v3.4-rc2. Attached is my kconfig.
>
> commit 77b0d60c5adf39c74039e2142a1d3cd1e4d53799
> Author: Suresh Siddha <suresh.b.siddha@intel.com>
> Date: Fri Nov 4 17:18:21 2011 -0700
>
> clockevents: Leave the broadcast device in shutdown mode when not needed
>
> Platforms with Always Running APIC Timer doesn't use the broadcast timer
> but the kernel is leaving the broadcast timer (HPET in this case)
> in oneshot mode.
>
> On these platforms, before the switch to oneshot mode, broadcast device is
> actually in shutdown mode. Code checks for empty tick_broadcast_mask and
> avoids going into the periodic mode.
>
> During switch to oneshot mode, add the same tick_broadcast_mask checks in the
> tick_broadcast_switch_to_oneshot() and avoid the broadcast device going into
> the oneshot mode.
>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
> Cc: john stultz <johnstul@us.ibm.com>
> Cc: venki@google.com
> Link: http://lkml.kernel.org/r/1320452301.15071.16.camel@sbsiddha-desk.sc.intel.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


It made loopback netperf performance regression on NHM-EP, I thought it
is due to few local timers missing on EP, but didn't know it is totally
out of work on EX.





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