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

>
>>      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);
>>
>>
>> _______________________________________________
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>> 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