Re: [Xen-devel] Scalable Event Channel ABI design (draft A)

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-02-05 at 15:54 +0000, David Vrabel wrote:
> On 05/02/13 15:49, Keir Fraser wrote:
> > On 05/02/2013 14:48, "David Vrabel" <david.vrabel@xxxxxxxxxx> 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.

VCPUOP_register_vcpu_info doesn't require each vcpu_info to be on a page
by itself, even if that happens to be the Linux implementation today (I
haven't checked that).

Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel