xl: expose max_cpu_id from `xl info`

xl: expose max_cpu_id from `xl info`

[Andrew Cooper]

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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


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# 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);
     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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Re: xl: expose max_cpu_id from `xl info`

[Zhigang Wang]

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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

>      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


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Re: xl: expose max_cpu_id from `xl info`

[Andrew Cooper]

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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);
>>
>>
>> _______________________________________________
>> 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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Re: xl: expose max_cpu_id from `xl info`

[Ian Jackson]

Andrew Cooper writes ("[Xen-devel] xl: expose max_cpu_id from `xl info`"):
> xl: display max_cpu_ids for xl info

Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

Re: xl: expose max_cpu_id from `xl info`

[Zhigang Wang]

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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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Re: xl: expose max_cpu_id from `xl info`

[Andrew Cooper]

<snip>
>>> 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
>
>

No.  The names here reflect the hypercall name parameters.  The
hypercall cant be changed because it is an ABI, and the "name : value"
pairs here cant be changed because of backward compatibility with the
previous toolstack.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com

Re: xl: expose max_cpu_id from `xl info`

[Zhigang Wang]

On 03/14/2012 12:24 PM, Andrew Cooper wrote:
> <snip>
>>>> 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
>>
>>
> No.  The names here reflect the hypercall name parameters.  The
> hypercall cant be changed because it is an ABI, and the "name : value"
> pairs here cant be changed because of backward compatibility with the
> previous toolstack.
>
Ok. Thanks for you info. I think nr_online_cpus() is the right thing here: it
represents online physical cpus from hypervisor's viewpoint.

It's fine to add this output here if  you need it. But for most of the xen
users, the current nr_cpus should be what they want (for how many pcpus they can
use).

Other ways to get full hardware info could be BIOS/SMBIOS/DMI, and I think it's
better than xl info.

Thanks,

Zhigang