On 30/08/18 10:43, Jan Beulich wrote:
>>>> On 30.08.18 at 10:31, <jgr...@suse.com> wrote:
>> On 30/08/18 10:16, Jan Beulich wrote:
>>>>>> On 29.08.18 at 20:23, <jgr...@suse.com> wrote:
>>>> The topology information obtainable via XEN_SYSCTL_cputopoinfo is
>>>> filled rather weird: the size of the array is derived from the highest
>>>> online cpu number, while the data is set to "invalid" for not present
>>>> cpus only.
>>>>
>>>> With smt=0 the information for parked threads is all zero, so it should
>>>> be best to return "invalid" information for offline cpus.
>>>>
>>>> On a dual core system without this patch xl info -n will print:
>>>>
>>>> cpu_topology :
>>>> cpu: core socket node
>>>> 0: 0 0 0
>>>> 1: 0 0 0
>>>> 2: 1 0 0
>>>
>>> But there's nothing wrong here. The interesting part is what would be
>>> printed for CPU 3 (perhaps on a more than two cores system). After
>>> all topology is valid irrespective of whether a CPU is online - it all
>>> depends on whether the hypervisor still has the information available.
>>> It is for a reason that cpu_smpboot_free() invalidates certain fields
>>> only upon CPU removal:
>>>
>>> if ( remove )
>>> {
>>> c[cpu].phys_proc_id = XEN_INVALID_SOCKET_ID;
>>> c[cpu].cpu_core_id = XEN_INVALID_CORE_ID;
>>> c[cpu].compute_unit_id = INVALID_CUID;
>>>
>>> On a 6-core system I see
>>>
>>> cpu: core socket node
>>> 0: 0 0 0
>>> 1: 0 0 0
>>> 2: 1 0 0
>>> 3: 1 0 0
>>> 4: 2 0 0
>>> 5: 2 0 0
>>> 6: 8 0 0
>>> 7: 8 0 0
>>> 8: 9 0 0
>>> 9: 9 0 0
>>> 10: 10 0 0
>>>
>>> which looks fine to me, apart from the missing info on CPU 11.
>>
>> I can change the patch to print the information for the offline cpus
>> (including the now missing ones), too.
>>
>> What is the preferred solution?
>
> Well, by implication from my earlier reply I think adding the missing
> CPU's info would be better. Let's see what others think.
Okay.
I'll do that and add another patch adding "(offline)" to the output in
case a cpu is offline.
Juergen
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