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

[Cornelia Huck]

On Tue, 22 Aug 2017 13:31:27 +0200
David Hildenbrand <david at 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.