linux-kernel - Re: [PATCH] kvm: add halt_poll

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Message-ID: <54D9B857.7080500@redhat.com>
Date:	Tue, 10 Feb 2015 08:50:47 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
CC:	riel@...hat.com, mtosatti@...hat.com, rkrcmar@...hat.com,
	jan.kiszka@...mens.com, dmatlack@...gle.com
Subject: Re: [PATCH] kvm: add halt_poll_ns module parameter



On 09/02/2015 22:00, Christian Borntraeger wrote:
> I can confirm that this also helps uperf with a 1/1 byte round trip work load
> between guests on s390. And I can confirm the higher CPU load. This is normally
> a no-go for the typical s390 users, which utilize their systems as much as 
> possible. Your check for single_task_running could actually solve that
> problem because on overcommitment this will never switch to polling if the
> runqueues get full.
> Since this is also runtime configurable and defaults to 0 it should be pretty
> painless.
> 
> The only question is: is there a sane way of doing autotuning?

The answer is: we'll see. :)  I have some ideas, I have to run them
through the necessary experiments.

Paolo
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