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Re: [Xen-devel] "cpus" config parameter broken?

To: "dan.magenheimer@xxxxxxxxxx" <dan.magenheimer@xxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] "cpus" config parameter broken?
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 10 Jan 2008 22:55:30 +0000
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Thread-topic: [Xen-devel] "cpus" config parameter broken?
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On 10/1/08 22:53, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> That doesn't play nicely with CPU hotplug (not supported yet,
>> but could well
>> be in future) where the online_map could be continually
>> changing. The model
>> I'm aiming for in Xen is to remember all the CPUs requested by the
>> toolstack, but only schedule onto the subset that are
>> actually online right
>> now (obviously). The implementation of this is of course
>> quite simple given
>> the CPU hotplug is not supported right now.
> 
> Agreed, but even with CPU hotplug there will be some max_pcpu value
> on any given machine.  That's why I said "non-existent processor"
> in the proposal even though you said "offline processor".

You mean CPUs beyond NR_CPUS? All the cpumask iterators are careful not to
return values beyond NR_CPUS, regardless of what stray bits lie beyond that
range in the longword bitmap.

 -- Keir



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