From: Peter Zijlstra <peterz@infradead.org>
To: dipankar@in.ibm.com
Cc: Len Brown <lenb@kernel.org>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
Trinabh Gupta <trinabh@linux.vnet.ibm.com>,
arjan@linux.intel.com, Stephen Rothwell <sfr@canb.auug.org.au>,
suresh.b.siddha@intel.com, benh@kernel.crashing.org,
venki@google.com, ak@linux.intel.com,
linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com
Subject: Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm)
Date: Tue, 05 Apr 2011 17:01:32 +0200 [thread overview]
Message-ID: <1302015692.2225.1347.camel@twins> (raw)
In-Reply-To: <20110404143259.GA11525@in.ibm.com>
On Mon, 2011-04-04 at 20:02 +0530, Dipankar Sarma wrote:
> On Fri, Apr 01, 2011 at 04:02:36PM +0200, Peter Zijlstra wrote:
> >
> > > S0i3 on cpu0 can be entered only after cpu1 is already off-line,
> > > among other system hardware dependencies...
> > >
> > > So it makes no sense to export S0i3 as a c-state on cpu1.
> > >
> > > When cpu1 is online, the scheduler treats it as a normal SMP.
> >
> > Dipankar's reply seems to address this issue well.
>
> I can't find any Moorestown documentation at the Intel site, but
> thinking about Len's inputs a bit more, it seems there may
> be still a problem asymetry from the scheduler perspective.
>
> If cpu0 or cpu1 either of them can be offlined, there is no
> asymetry. If only cpu1 can be offlined, it would mean that
> one cpu may be more efficient depending on how we do
> cpu offlining for power savings. It gets a bit messy.
>
> Len, what exacty is the significance of offlining here ?
> Apart from going to C6, what else is needed in cpu1 for
> the chip to go to S0i3 ? Why is idle C6 not enough ?
I don't think offlining is relevant, anybody using that for power
management is doing it wrong, _very_ wrong.
next prev parent reply other threads:[~2011-04-05 15:01 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-22 12:32 [RFC PATCH V4 0/5] cpuidle: Cleanup pm_idle and include driver/cpuidle.c in-kernel Trinabh Gupta
2011-03-22 12:32 ` [RFC PATCH V4 1/5] cpuidle: Remove pm_idle pointer for x86 Trinabh Gupta
2011-03-23 1:00 ` Stephen Rothwell
2011-03-23 10:10 ` Trinabh Gupta
2011-03-22 12:32 ` [RFC PATCH V4 2/5] cpuidle: list based cpuidle driver registration and selection Trinabh Gupta
2011-03-23 2:59 ` Len Brown
2011-03-23 9:22 ` Trinabh Gupta
2011-03-23 20:51 ` Len Brown
2011-03-24 4:41 ` Len Brown
2011-03-24 14:13 ` Trinabh Gupta
2011-03-24 16:52 ` Vaidyanathan Srinivasan
2011-03-25 7:13 ` Len Brown
2011-03-25 7:05 ` Len Brown
2011-03-25 15:35 ` [Xen-devel] " Konrad Rzeszutek Wilk
2011-03-31 2:25 ` Len Brown
2011-03-22 12:33 ` [RFC PATCH V4 3/5] cpuidle: default idle driver for x86 Trinabh Gupta
2011-03-23 3:13 ` Len Brown
2011-03-23 9:31 ` Trinabh Gupta
2011-03-24 16:32 ` Vaidyanathan Srinivasan
2011-03-22 12:33 ` [RFC PATCH V4 4/5] cpuidle: driver for xen Trinabh Gupta
2011-03-22 14:50 ` Konrad Rzeszutek Wilk
2011-03-23 9:57 ` Trinabh Gupta
2011-03-24 7:18 ` Len Brown
2011-03-24 12:05 ` Konrad Rzeszutek Wilk
2011-03-25 7:19 ` Len Brown
2011-03-25 14:43 ` [Xen-devel] " Jeremy Fitzhardinge
2011-03-25 14:38 ` Jeremy Fitzhardinge
2011-03-31 2:02 ` Len Brown
2011-03-31 21:26 ` Len Brown
2011-03-31 22:36 ` Jeremy Fitzhardinge
2011-04-01 3:03 ` Len Brown
2011-03-22 12:33 ` [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm Trinabh Gupta
2011-03-23 1:14 ` Stephen Rothwell
2011-03-23 10:25 ` Trinabh Gupta
2011-03-23 20:32 ` Len Brown
2011-03-24 14:28 ` Trinabh Gupta
2011-03-24 16:21 ` Vaidyanathan Srinivasan
2011-03-25 7:24 ` Len Brown
2011-03-25 18:01 ` Vaidyanathan Srinivasan
2011-03-31 2:17 ` cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm) Len Brown
2011-03-31 13:18 ` Peter Zijlstra
2011-04-01 4:09 ` Len Brown
2011-04-01 8:15 ` Dipankar Sarma
2011-04-01 14:38 ` Arjan van de Ven
2011-04-03 16:18 ` Dipankar Sarma
2011-04-01 14:02 ` Peter Zijlstra
2011-04-04 14:32 ` Dipankar Sarma
2011-04-05 15:01 ` Peter Zijlstra [this message]
2011-04-05 15:48 ` Dipankar Sarma
2011-04-01 7:02 ` Trinabh Gupta
2011-03-24 4:27 ` [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm Len Brown
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