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[Xen-devel] Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: c

To: dipankar@xxxxxxxxxx
Subject: [Xen-devel] Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidle driver for apm)
From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Date: Fri, 01 Apr 2011 07:38:23 -0700
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>, ak@xxxxxxxxxxxxxxx, suresh.b.siddha@xxxxxxxxx, venki@xxxxxxxxxx, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, benh@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx>, Trinabh Gupta <trinabh@xxxxxxxxxxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>
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On 4/1/2011 1:15 AM, Dipankar Sarma wrote:
On Fri, Apr 01, 2011 at 12:09:25AM -0400, Len Brown wrote:
Moorestown is already an example of an asymmetric system,
since its deepest c-state is available on cpu0, but not on cpu1.
So it needs different tables for each cpu.
wtf are these hardware guys smoking and how the heck are we supposed to
schedule on such a machine? Prefer to keep cpu1 busy while idling cpu0?
they are smoking micro-amps:-)

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.
Isn't S0i3 a "system" state, as opposed to cpu state ?

it's misnamed. it's a C state to the OS.

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