Re: [Xen-devel] [PATCH v6 4/7] x86: collect CQM information from all sockets

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.01.14 at 15:34, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 28/01/14 14:23, Xu, Dongxiao wrote:
>>> And finally, I think the total size of the buffer here can easily
>>> exceed a page, i.e. this then ends up being a non-order-0
>>> allocation, which may _never_ succeed (i.e. the operation is
>>> then rendered useless). I guest it'd be better to e.g. vmap()
>>> the MFNs underlying the guest buffer.
>> Do you mean we check the size of the total size, and allocate MFNs one by 
> one, then vmap them?
> 
> I still think this is barking mad as a method of getting this quantity
> of data from Xen to the toolstack in a repeated fashon.
> 
> Xen should allocate a per-socket buffer at the start of day (or perhaps
> on first use of CQM), and the CQM monitoring tool gets to map those
> per-socket buffers read-only.
> 
> This way, all processing of the CQM data happens in dom0 userspace, not
> in Xen in hypercall context; All Xen has to do is periodically dump the
> MSRs into the pages.

Indeed - if the nature of the data is such that it can be exposed
read-only to suitably privileged entities, then this would be the
much better interface.

Jan


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