linux-kernel - Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework

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Date:	Tue, 15 Sep 2009 23:21:51 +1000
From:	Michael Ellerman <michael@...erman.id.au>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Gautham R Shenoy <ego@...ibm.com>, linux-kernel@...r.kernel.org,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org,
	"Darrick J. Wong" <djwong@...ibm.com>
Subject: Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework

On Tue, 2009-09-15 at 14:11 +0200, Peter Zijlstra wrote:
> On Tue, 2009-09-15 at 17:36 +0530, Gautham R Shenoy wrote:
> > This patchset contains the offline state driver implemented for
> > pSeries. For pSeries, we define three available_hotplug_states. They are:
> > 
> >         online: The processor is online.
> > 
> >         offline: This is the the default behaviour when the cpu is offlined
> >         even in the absense of this driver. The CPU would call make an
> >         rtas_stop_self() call and hand over the CPU back to the resource pool,
> >         thereby effectively deallocating that vCPU from the LPAR.
> >         NOTE: This would result in a configuration change to the LPAR
> >         which is visible to the outside world.
> > 
> >         inactive: This cedes the vCPU to the hypervisor with a cede latency
> >         specifier value 2.
> >         NOTE: This option does not result in a configuration change
> >         and the vCPU would be still entitled to the LPAR to which it earlier
> >         belong to.
> > 
> > Any feedback on the patchset will be immensely valuable.
> 
> I still think its a layering violation... its the hypervisor manager
> that should be bothered in what state an off-lined cpu is in. 

Yeah it probably is a layering violation, but when has that stopped us
before :)

Is it anticipated that this will be useful on platforms other than
pseries?

cheers



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