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Re: [Xen-devel] Cache Allocation Technology(CAT) design for XEN

>>> On 16.12.14 at 09:55, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> Any comments from you? It would be greatly appreciated if you can look
> at this when you have time. Your comments are always important to me :)

I don't think I have to say much here:

> On Fri, Dec 12, 2014 at 08:27:57PM +0800, Chao Peng wrote:
>> Implementation Description
>> ==========================
>> In this design, one principal is that only implementing the cache
>> enforcement mechanism in hypervisor but leaving the cache allocation
>> policy to user space tool stack. In this way some complex governors then
>> can be implemented in tool stack. 

With this, the changes to the hypervisor ought to be quite limited,
even if length of the list you give seems long at a first glance, and
hence I'm fine with the concept.

>> Hardware Limitation & Performance Improvement
>> =============================================
>> As the COS of PCPU in IA32_PQR_ASSOC is changed on each VCPU context
>> switch. If the change is frequent then hardware may fail to strictly
>> enforce the cache allocation basing on the specified COS.

This certainly would deserve a little more explanation: What's the
value of the functionality if one can't rely on it being enforced by
hardware at all times?


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