Re: Scalable Event Channel ABI design (draft A)

[David Vrabel <david.vrabel@citrix.com>]

On 05/02/13 15:49, Keir Fraser wrote:
> On 05/02/2013 14:48, "David Vrabel" <david.vrabel@citrix.com> wrote:
> 
>>> I have some sympathy for this design. It's primary downside compared with
>>> the 3-level alternative is its greater space cost (32*#vcpus). However, as
>>> you say the fairness and prioritisation features are rather nice. Also
>>> having the data structures be per vcpu may well help avoid cacheline
>>> contention on busy multi-vcpu guests.
>>
>> This design originally (before I posted it) did have per-VCPU event
>> arrays but I changed it to per-domain to reduce the memory footprint.
> 
> Okay, I wonder how much it actually matters anyhow...
> 
> Oh by the way you say the control block is 128 bytes and will easily fit in
> the existing struct vcpu_info. That existing structure is 64 bytes in total.
> So how does that work then?

I meant struct vcpu_info can be extended without it growing to more than
a page.  i.e., it fits into the guest page provided in the
VCPUOP_register_vcpu_info call so no additional pages need to be
globally mapped for the control block.

David