From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cornelia Huck <cornelia.huck@de.ibm.com>
Subject: Re: [PATCH/RFC] KVM: halt_polling: provide a way to qualify wakeups
 during poll
Date: Mon, 2 May 2016 13:46:27 +0200
Message-ID: <20160502134627.71319e1b.cornelia.huck@de.ibm.com>
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Radim =?UTF-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>, KVM <kvm@vger.kernel.org>, linux-s390 <linux-s390@vger.kernel.org>, Jens Freimann <jfrei@linux.vnet.ibm.com>, David Hildenbrand <dahi@linux.vnet.ibm.com>
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On Mon,  2 May 2016 12:42:33 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:


> @@ -2038,14 +2039,16 @@ out:
>  		if (block_ns <= vcpu->halt_poll_ns)
>  			;
>  		/* we had a long block, shrink polling */
> -		else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
> +		else if (!vcpu_valid_wakeup(vcpu) ||
> +			(vcpu->halt_poll_ns && block_ns > halt_poll_ns))
>  			shrink_halt_poll_ns(vcpu);
>  		/* we had a short halt and our poll time is too small */
>  		else if (vcpu->halt_poll_ns < halt_poll_ns &&
> -			block_ns < halt_poll_ns)
> +			block_ns < halt_poll_ns && vcpu_valid_wakeup(vcpu))

Isn't that vcpu_valid_wakeup() check superflous, as we have collected
all !vcpu_valid_wakeup() cases in the previous if?

>  			grow_halt_poll_ns(vcpu);
>  	} else
>  		vcpu->halt_poll_ns = 0;
> +	vcpu_reset_wakeup(vcpu);
> 
>  	trace_kvm_vcpu_wakeup(block_ns, waited);
>  }