Re: Question about the CAT and CMT in Xen

[Meng Xu <xumengpanda@gmail.com>]

2015-09-01 10:30 GMT-04:00 Andrew Cooper <andrew.cooper3@citrix.com>:
> On 01/09/15 15:20, Meng Xu wrote:
>> 2015-09-01 9:04 GMT-04:00 Andrew Cooper <andrew.cooper3@citrix.com>:
>>> On 01/09/15 13:55, Meng Xu wrote:
>>>> 2015-09-01 1:47 GMT-04:00 Chao Peng <chao.p.peng@linux.intel.com>:
>>>>> On Mon, Aug 31, 2015 at 04:09:31PM -0400, Meng Xu wrote:
>>>>>> I looked into the xen/arch/x86/psr.c and found that the function
>>>>>> cat_cpu_init() just returned without initializing the variable
>>>>>> "cat_socket_enable".
>>>>>>
>>>>>> Both  !cpu_has(c, X86_FEATURE_CAT) and c->cpuid_level <
>>>>>> PSR_CPUID_LEVEL_CAT are evaluated as 1 inside the function
>>>>>> cat_cpu_init().
>>>>>>
>>>>>> OK. I understand that  the cpuid info shows that the CPU does not
>>>>>> support CAT. However, according to the table at
>>>>>> http://www.intel.com/content/www/us/en/communications/cache-monitoring-cache-allocation-technologies.html,
>>>>>>  Intel(R) Xeon(R) CPU E5-2618L v3 should support CAT.
>>>>>>
>>>>>> I'm not sure which part is incorrect: the hardware or the software?
>>>>>> (Hope Chao could give some insight about this.)
>>>>>>
>>>>> Hmmm, from cpuid info it looks like this model does not support CAT. I'm
>>>>> not sure which microarchitecture it is.
>>>> According to http://www.cpu-world.com/CPUs/Xeon/Intel-Xeon%20E5-2618L%20v3.html,
>>>> 2618L v3 is Haswell. :-(
>>> Wikipedia agrees.
>>>
>>> Haswell only has plain L3 cache usage information.
>>>
>>> It is Broadwell which adds memory bandwidth monitoring, and Cache
>>> Allocation.
>> Ah, then the Intel's website [1] that lists the CAT-enabled processor
>> is quite misleading. I checked several processors (2618Lv3, 2608Lv3,
>> 2658v3) listed  in [1] that is claimed to have CAT, and all of them
>> belong to Haswell... I think "v3" actually represents Haswell.
>>
>> Andrew, is it possible to know which processor XenServer is currently
>> using that is confirmed to have the CAT mechanism?
>
> I cant be much help, unfortunately,

Thank you very much for your trying to help! :-)

Hope Chao could give more information about which Intel processors
support the CAT.

Best,

Meng



-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/