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Re: [Xen-devel] [PATCH][RESUBMIT] don't schedule unplugged vcpus

To: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][RESUBMIT] don't schedule unplugged vcpus
From: Ryan Harper <ryanh@xxxxxxxxxx>
Date: Wed, 8 Jun 2005 16:52:44 -0500
Cc: Ryan Harper <ryanh@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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* Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx> [2005-06-08 16:44]:
> > I've added in changes to DOM0_GETDOMINFO and 
> > DOM0_GETVCPUCONTEXT hypercalls.  dominfo now creates a 
> > vcpu_online_map bitmap which marks whether vcpus are up or 
> > down.  I didn't want to clobber either the total number of 
> > vcpus allocated to a domain (n_vcpu) nor the vcpu_to_cpu 
> > mapping since both are still valid whether the vcpu is being 
> > scheduled or not.
> I don't see why we care about vcpus that are down. From the user's point
> of view they've gone for good -- it just happens that Xen hasn't freed
> the memory in anticipation of it being used again. What do you think?

I don't think the users care so much as I want tools to be able to
extract the current state of affairs for load balancing or other
operations that want to account for domain state.

> I'd be inclined just to enter '-1' in the vcpu_to_cpu map. BTW: we could
> make it an s16 rather than s32 at the same time. I think 32,768 CPUs
> should keep be enough for anyone :-) 


Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253

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