Re: [PATCH v3 11/14] libxl: get and set soft affinity

[George Dunlap <george.dunlap@eu.citrix.com>]

On 19/11/13 16:09, Dario Faggioli wrote:
> On mar, 2013-11-19 at 15:41 +0000, George Dunlap wrote:
>> On 11/18/2013 06:18 PM, Dario Faggioli wrote:
>>> Make space for two new cpumap-s, one in vcpu_info (for getting
>>> soft affinity) and build_info (for setting it). Provide two
>>> new API calls:
>>>
>>>    * libxl_set_vcpuaffinity2, taking a cpumap and setting either
>>>      hard, soft or both affinity to it, depending on 'flags';
>>>    * libxl_set_vcpuaffinity3, taking two cpumap, one for hard
>>>      and one for soft affinity.
>>>
>>> The bheavior of the existing libxl_set_vcpuaffinity is left
>>> unchanged, i.e., it only set hard affinity.
>>>
>>> Getting soft affinity happens indirectly, via `xl vcpu-list'
>>> (as it is already for hard affinity).
>>>
>>> The new calls include logic to check whether the affinity which
>>> will be used by Xen to schedule the vCPU(s) does actually match
>>> with the cpumap provided. In fact, we want to allow every possible
>>> combination of hard and soft affinities to be set, but we warn
>>> the user upon particularly weird combinations (e.g., hard and
>>> soft being disjoint sets of pCPUs).
>>>
>>> Also, this is the first change breaking the libxl ABI, so it
>>> bumps the MAJOR.
>>>
>>> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
>> The interface is fine with me (I would probably just have 2 and not 3,
>> but I'm OK with both).  Just a few minor comments:
>>
> the '3' variant (tries to) accomplish what IanJ explicitly asked: having
> a way to set both hard and soft affinity at the same time, and each with
> its own value, and only checking for consistency at the very end.
>
> I also wasn't sure whether that would have been actually useful but, I
> have to admit, it turned out it is, as it can be seen in the following
> patches, when the interface is used to (re)implement both the existing
> and the new xl commands and command variants.
>
> Let's see what IanJ thinks, I guess. :-)

BTW, I wasn't complaining -- I know IanJ wanted it the second way; I was 
just re-registering my preference.  :-)

  -George