linux-kernel - Re: [PATCH] cpuidle: powernv/pseries: Decrease the snooze residency

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Date:	Sat, 30 May 2015 20:38:22 -0500
From:	Benjamin Herrenschmidt <benh@....ibm.com>
To:	svaidy@...ux.vnet.ibm.com
Cc:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	linux-pm@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>, rjw@...ysocki.net,
	linux-kernel@...r.kernel.org, anton@...ba.org,
	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] cpuidle: powernv/pseries: Decrease the snooze residency

On Sat, 2015-05-30 at 11:31 +0530, Vaidyanathan Srinivasan wrote:
> In shared lpar case, spinning in guest context may potentially take
> away cycles from other lpars waiting to run on the same physical cpu.
> 
> So the policy in shared lpar case is to let PowerVM hypervisor know
> immediately that the guest cpu is idle which will allow the hypervisor
> to use the cycles for other tasks/lpars.

But that will have negative side effects under KVM no ?

Suresh mentioned something with his new directed interrupts code that we
had many cases where the interrupts ended up arriving shortly after we
exited to host for NAP'ing ...

Snooze might fix it...

Ben.


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