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?
Juergen
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