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

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@xxxxxxxxxx>
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. :-)


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