Re: [Xen-devel] Question about the CAT and CMT in Xen

[Meng Xu <xumengpanda@xxxxxxxxx>]

2015-09-01 9:04 GMT-04:00 Andrew Cooper <andrew.cooper3@xxxxxxxxxx>:
> On 01/09/15 13:55, Meng Xu wrote:
>> 2015-09-01 1:47 GMT-04:00 Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>:
>>> 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?

Thank you very much!

Best,

[1] 
http://www.intel.com/content/www/us/en/communications/cache-monitoring-cache-allocation-technologies.html

Meng

-- 


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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel