From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v2 2/4] sysctl: Make XEN_SYSCTL_topologyinfo
 sysctl a little more efficient
Date: Wed, 07 Jan 2015 09:45:14 -0500
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To: Jan Beulich <JBeulich@suse.com>, Andrew Cooper <andrew.cooper3@citrix.com>
Cc: wei.liu2@citrix.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, dario.faggioli@citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, ufimtseva@gmail.com, keir@xen.org
List-Id: xen-devel@lists.xenproject.org

On 01/07/2015 04:12 AM, Jan Beulich wrote:
>>>> On 06.01.15 at 14:41, <andrew.cooper3@citrix.com> wrote:
>> On 06/01/15 02:18, Boris Ostrovsky wrote:
>>> Instead of copying data for each field in xen_sysctl_topologyinfo separately
>>> put cpu/socket/node into a single structure and do a single copy for each
>>> processor.
>>>
>>> There is also no need to copy whole op to user at the end, max_cpu_index is
>>> sufficient
>>>
>>> Rename xen_sysctl_topologyinfo and XEN_SYSCTL_topologyinfo to reflect the fact
>>> that these are used for CPU topology. Subsequent patch will add support for
>>> PCI topology sysctl.
>>>
>>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>> If we are going to change the hypercall, then can we see about making it
>> a stable interface (i.e. not a sysctl/domctl)?  There are non-toolstack
>> components which might want/need access to this information.  (i.e. I am
>> still looking for a reasonable way to get this information from Xen in
>> hwloc)
> In which case leaving the sysctl alone and just adding a new non-sysctl
> interface should be considered.

I'd expect IO NUMA information to be used together with CPU topology 
information so I am not sure how useful this would be. Unless we create 
a similar interface for that (CPU/memory) as well.

-boris