linux-kernel - Re: [PATCH v2] KVM: halt-polling: poll if emulated lapic timer will fire soon

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Message-ID: <d7657003-0321-2e4d-6a55-bc7a70e85aca@redhat.com>
Date:	Thu, 19 May 2016 16:56:55 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>,
	Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc:	Wanpeng Li <wanpeng.li@...mail.com>,
	Radim Krčmář <rkrcmar@...hat.com>,
	David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH v2] KVM: halt-polling: poll if emulated lapic timer will
 fire soon



On 19/05/2016 16:52, Christian Borntraeger wrote:
>> > Would this work too and be simpler?
> Hmm, your patch does only fiddle with the grow/shrink logic (which might
> be a good idea independently of this change), but the original patch 
> actually takes into account that we have a guaranteed maximum time by a 
> wakeup timer - IOW we know exactly what the maximum poll time is.
> 

Yes, it's different.  The question is whether a 10us poll (40,000 clock
cycles) has an impact even if it's sometimes wrong.

Thanks,

Paolo