From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [PATCH RESEND 05/12] xen: numa-sched: make space
 for per-vcpu node-affinity
Date: Tue, 5 Nov 2013 15:11:15 +0000
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To: Jan Beulich <JBeulich@suse.com>
Cc: Marcus Granado <Marcus.Granado@eu.citrix.com>, Justin Weaver <jtweaver@hawaii.edu>, Ian Campbell <Ian.Campbell@citrix.com>, Li Yechen <lccycc123@gmail.com>, Andrew Cooper <Andrew.Cooper3@citrix.com>, Dario Faggioli <dario.faggioli@citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Matt Wilson <msw@amazon.com>, xen-devel <xen-devel@lists.xenproject.org>, Daniel De Graaf <dgdegra@tycho.nsa.gov>, Keir Fraser <keir@xen.org>, Elena Ufimtseva <ufimtseva@gmail.com>, Juergen Gross <juergen.gross@ts.fujitsu.com>
List-Id: xen-devel@lists.xenproject.org

On 11/05/2013 03:03 PM, George Dunlap wrote:
> On 11/05/2013 02:52 PM, Jan Beulich wrote:
>>>>> On 05.11.13 at 15:35, Dario Faggioli <dario.faggioli@citrix.com>
>>>>> wrote:
>>> @@ -197,6 +199,13 @@ struct vcpu
>>>       /* Used to restore affinity across S3. */
>>>       cpumask_var_t    cpu_affinity_saved;
>>>
>>> +    /*
>>> +     * Bitmask of CPUs on which this VCPU prefers to run. For both this
>>> +     * and auto_node_affinity access is serialized against
>>> +     * v->domain->node_affinity_lock.
>>> +     */
>>> +    cpumask_var_t    node_affinity;
>>
>> This all looks quite sensible, except for the naming here: We
>> already have a node_affinity field in struct domain, having a
>> meaning that one can expect with this name. So you break
>> both consistency and the rule of least surprise here. How
>> about just "preferred_cpus"?
>
> Actually, would it make more sense to remove node_affinity from the
> domain struct, and have the tools manually set the node_affinity for the
> various vcpus if the user attempts to set the "domain numa affinity"?

Sorry, speaking before I had thought it through.  Of course we need a 
numa affinity for the domain for allocating memory.

How about, "cpu_node_affinity"?

Or, we could internally change the names to "cpu_hard_affinity" and 
"cpu_soft_affinity", since that's effectively what the scheduler will 
do.  It's possible someone might want to set soft affinities for some 
other reason besides NUMA performance.

  -George