Re: [Xen-devel] [PATCH] SEDF: avoid gathering vCPU-s on pCPU0

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 04/03/13 11:37, Jan Beulich wrote:
> While you might argue that affinity changes ought to be done
> in a "sensible" way, I think you still realize that there is behavior
> here that one wouldn't be able to control without explicitly
> adding an intermediate step when doing this for DomU-s. And
> you should also keep in mind that there are certain things that
> Dom0 needs to change its vCPU affinities for (pv-ops doesn't
> do that, which is while certain things there just can't work);
> this is how I noticed in the first place that the second half of
> the fix is necessary.
Oh right -- so the problem is that when you *expand* the mask, you want 
the scheduler to take another look at where might be a good place to run 
the vcpu given the changed constraints.
It's probably not a bad idea to just extend that idea to all the 
schedulers really.  It's not like we expect people to be changing the 
affinity masks hundreds of times a second.
 -George

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