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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: dipankar@in.ibm.com
Cc: Gautham R Shenoy <ego@in.ibm.com>,
	Joel Schopp <jschopp@austin.ibm.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Balbir Singh <balbir@in.ibm.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Arun R Bharadwaj <arun@linux.vnet.ibm.com>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	"Darrick J. Wong" <djwong@us.ibm.com>
Subject: Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework
Date: Wed, 16 Sep 2009 17:32:51 +0200	[thread overview]
Message-ID: <1253115171.7180.1.camel@laptop> (raw)
In-Reply-To: <20090916152820.GA12571@in.ibm.com>

On Wed, 2009-09-16 at 20:58 +0530, Dipankar Sarma wrote:
> On Tue, Sep 15, 2009 at 02:11:41PM +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
> > > 
> > >         inactive: This cedes the vCPU to the hypervisor with a cede latency
> > > 
> > > 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. 
> 
> The problem is that all hypervisor managers cannot figure out what sort
> of latency guest OS can tolerate under the situation. They wouldn't know
> from what context guest OS has ceded the vcpu. It has to have
> some sort of hint, which is what the guest OS provides.

I'm missing something here, hot-unplug is a slow path and should not
ever be latency critical..?


WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: dipankar@in.ibm.com
Cc: Gautham R Shenoy <ego@in.ibm.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
	linux-kernel@vger.kernel.org,
	Arun R Bharadwaj <arun@linux.vnet.ibm.com>,
	linuxppc-dev@lists.ozlabs.org,
	"Darrick J. Wong" <djwong@us.ibm.com>
Subject: Re: [PATCH v3 0/3] cpu: pseries: Cpu offline states framework
Date: Wed, 16 Sep 2009 17:32:51 +0200	[thread overview]
Message-ID: <1253115171.7180.1.camel@laptop> (raw)
In-Reply-To: <20090916152820.GA12571@in.ibm.com>

On Wed, 2009-09-16 at 20:58 +0530, Dipankar Sarma wrote:
> On Tue, Sep 15, 2009 at 02:11:41PM +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
> > > 
> > >         inactive: This cedes the vCPU to the hypervisor with a cede latency
> > > 
> > > 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. 
> 
> The problem is that all hypervisor managers cannot figure out what sort
> of latency guest OS can tolerate under the situation. They wouldn't know
> from what context guest OS has ceded the vcpu. It has to have
> some sort of hint, which is what the guest OS provides.

I'm missing something here, hot-unplug is a slow path and should not
ever be latency critical..?

  reply	other threads:[~2009-09-16 15:33 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-09-15 12:06 [PATCH v3 0/3] cpu: pseries: Cpu offline states framework Gautham R Shenoy
2009-09-15 12:07 ` [PATCH v3 1/3] pSeries: cede latency specifier helper function Gautham R Shenoy
2009-09-15 14:45   ` Daniel Walker
2009-09-15 14:45     ` Daniel Walker
2009-09-15 12:07 ` [PATCH v3 2/3] cpu: Offline state Framework Gautham R Shenoy
2009-09-30 17:31   ` Randy Dunlap
2009-09-30 17:31     ` Randy Dunlap
2009-09-15 12:07 ` [PATCH v3 3/3] cpu: Implement cpu-offline-state callbacks for pSeries Gautham R Shenoy
2009-09-15 12:11 ` [PATCH v3 0/3] cpu: pseries: Cpu offline states framework Peter Zijlstra
2009-09-15 12:11   ` Peter Zijlstra
2009-09-15 13:21   ` Michael Ellerman
2009-09-15 14:58   ` Balbir Singh
2009-09-15 14:58     ` Balbir Singh
2009-09-16  7:48     ` Heiko Carstens
2009-09-16  7:48       ` Heiko Carstens
2009-09-24  0:52       ` Benjamin Herrenschmidt
2009-09-24  0:52         ` Benjamin Herrenschmidt
2009-09-16 15:28   ` Dipankar Sarma
2009-09-16 15:28     ` Dipankar Sarma
2009-09-16 15:32     ` Peter Zijlstra [this message]
2009-09-16 15:32       ` Peter Zijlstra
2009-09-16 16:24       ` Dipankar Sarma
2009-09-16 16:24         ` Dipankar Sarma
2009-09-16 16:35         ` Peter Zijlstra
2009-09-16 16:35           ` Peter Zijlstra
2009-09-16 17:03           ` Vaidyanathan Srinivasan
2009-09-16 17:03             ` Vaidyanathan Srinivasan
2009-09-16 17:22             ` Peter Zijlstra
2009-09-16 17:22               ` Peter Zijlstra
2009-09-16 20:17               ` Dipankar Sarma
2009-09-16 20:17                 ` Dipankar Sarma
2009-09-24  0:55         ` Benjamin Herrenschmidt
2009-09-24  0:55           ` Benjamin Herrenschmidt
2009-09-24  0:51   ` Benjamin Herrenschmidt
2009-09-24  0:51     ` Benjamin Herrenschmidt
2009-09-25 14:48     ` Peter Zijlstra
2009-09-25 14:48       ` Peter Zijlstra
2009-09-25 21:12       ` Benjamin Herrenschmidt
2009-09-25 21:12         ` Benjamin Herrenschmidt
2009-09-28 13:53         ` Vaidyanathan Srinivasan
2009-09-28 13:53           ` Vaidyanathan Srinivasan
2009-09-28 13:51       ` Vaidyanathan Srinivasan
2009-09-28 13:51         ` Vaidyanathan Srinivasan
2009-09-26  9:55   ` Pavel Machek
2009-09-26  9:55     ` Pavel Machek

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