Re: [Xen-devel] vCPU pinning

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I would like to "pin" vcpu to a domain,
> Can someone please point to me if there's such a support?

Your question didn't quite make sense, but I think I see what you mean - it's 
just that the terminology is a bit complicated!

If you consider a domain as being "like a process" then VCPUs are 
like "threads".  They're the parts of the domain that get scheduled on the 
real CPUs and do work.  *within* the domain, these will be shared out between 
processes the OS is running but /Xen doesn't really know about this/.  It 
just sees a bunch of VCPUs from a domain that it can run, and a bunch of real 
logical CPUs that it can run them on.

You can pin a VCPU to a real logical CPU (that's a core or a hyperthread on 
the host machine).  This can be used to divide up the machine more strictly, 
enforce separation or quality of service, etc.

You can specify pinning at runtime using the command "xm vcpu-pin", or in the 
domain config file using the "CPUs" variable.  I believe it's possible to set 
a mask of "possible CPUs" for all VCPUs or for individual VCPUs.

Hope this helps you.

Cheers,
Mark

PS. "how do I...?" questions are generally better directed to the xen-users 
mailing list - they're liable to get more responses and discussion there due 
to the higher subscriber cound and user focus.

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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