Re: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started vcpus

From	Cornelia Huck <cohuck@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started vcpus
Date	2017-08-29 13:30 +0200
Message-ID	<ujMSt-1Zf-7@gated-at.bofh.it> (permalink)
References	<uh1El-Dw-3@gated-at.bofh.it> <uh1El-Dw-15@gated-at.bofh.it> <uhfHk-1Ib-5@gated-at.bofh.it>
Organization	Red Hat GmbH

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On Tue, 22 Aug 2017 13:31:27 +0200
David Hildenbrand <david@redhat.com> wrote:

> On 21.08.2017 22:35, Radim Krčmář wrote:
> > We can add a variable instead of scanning all online VCPUs to know how
> > many are started.  We can't trivially tell which VCPU is the last one,
> > though.  
> 
> You could keep the started vcpus in a list. Then you might drop unsigned
> started_vcpus;
> 
> No started vcpus: Start pointer NULL
> Single started vcpu: Only one element in the list (easy to check)
> > 1 started vcpus: More than one element int he list (easy to check)  

I'm not sure the added complication of keeping a list buys us much
here: We only have the "look for the last vcpu not stopped" operation
for the 2->1 transition.

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Re: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started  vcpus Cornelia Huck <cohuck@redhat.com> - 2017-08-29 13:30 +0200
  Re: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started vcpus David Hildenbrand <david@redhat.com> - 2017-08-29 14:10 +0200
    Re: [PATCH RFC v3 1/9] KVM: s390: optimize detection of started  vcpus Cornelia Huck <cohuck@redhat.com> - 2017-08-29 14:50 +0200

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