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Re: [Xen-devel] pv_ops (2.6.31) and CONFIG_NO_HZ

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] pv_ops (2.6.31) and CONFIG_NO_HZ
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 02 Nov 2009 21:51:24 +0000
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
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Thread-topic: [Xen-devel] pv_ops (2.6.31) and CONFIG_NO_HZ
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Periodic ticks are disabled for non-running PV guests, so I don't think
no-hz has as much potential win as you might think.

 -- Keir

On 02/11/2009 21:45, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> Has anyone looked at using CONFIG_NO_HZ with an upstream
> pv_ops kernel?  This seems like an intelligent combination...
> since pvclock is a good timesource, it seems like there
> should be no reason to have a regular tick, and one
> could pack more idle domains into one physical machine.
> I tried enabling CONFIG_NO_HZ from an otherwise working .config
> file for 2.6.31 and the new kernel (running as a PV domU) panics early
> in boot ("Kernel panic -- not syncing: Attempted to kill init!"
> with a call trace of syscall_call->sys_exit_group->do_group_exit->
> do_exit->panic).  So I'm wondering if I did something stupid
> or it is known to not work.
> Thanks,
> Dan
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