Re: xl: expose max_cpu_id from `xl info`

[Zhigang Wang <zhigang.x.wang@oracle.com>]

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On 03/14/2012 06:45 AM, Andrew Cooper wrote:
> On 13/03/12 19:15, Zhigang Wang wrote:
>> On 03/13/2012 12:52 PM, Andrew Cooper wrote:
>>> This will allow userspace to reason with the total number of CPUs, not
>>> just the current number of online CPUs.
>>>
>>> -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225
>>> 900, http://www.citrix.com
>>>
>>> xl-info-max_cpu_id.patch
>>>
>>>
>>> # HG changeset patch
>>> # Parent 5d20d2f6ffed0a49f030f04a8870f1926babbcbf
>>> xl: display max_cpu_ids for xl info
>>>
>>> Expose "max_cpu_id" in stdout from `xl info`
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>>
>>> diff -r 5d20d2f6ffed tools/libxl/xl_cmdimpl.c
>>> --- a/tools/libxl/xl_cmdimpl.c
>>> +++ b/tools/libxl/xl_cmdimpl.c
>>> @@ -3734,6 +3734,7 @@ static void output_physinfo(void)
>>>      }
>>>  
>>>      printf("nr_cpus                : %d\n", info.nr_cpus);
>>> +    printf("max_cpu_id             : %d\n", info.max_cpu_id);
>>
>> Is this true: nr_cpus = max_cpu_id + 1 ?
>>
>> Zhigang
>
> if and only if all cpus are online.
>
> nr_cpus is set to nr_online_cpus() in the hypercall, while max_cpu_id is set
> to nr_cpu_ids-1.
>
> nr_cpus is liable to change during runtime, while max_cpu_id is not.
>
> ~Andrew

If this is the case, I think nr_cpus is a bit confusing. Can we make it always
representing the number of physical cpus (from hypervisor's viewpoint, not dom0)?

Zhigang

>
>>
>>>      printf("nr_nodes               : %d\n", info.nr_nodes);
>>>      printf("cores_per_socket       : %d\n", info.cores_per_socket);
>>>      printf("threads_per_core       : %d\n", info.threads_per_core);
>>>
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xen.org
>>> http://lists.xen.org/xen-devel
>>
>
> -- 
> Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
> T: +44 (0)1223 225 900, http://www.citrix.com


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