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

[Meng Xu <xumengpanda@xxxxxxxxx>]

2015-09-01 21:47 GMT-04:00 Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>:
> On Tue, Sep 01, 2015 at 10:42:57AM -0400, Meng Xu wrote:
>> 2015-09-01 10:30 GMT-04:00 Andrew Cooper <andrew.cooper3@xxxxxxxxxx>:
>> > On 01/09/15 15:20, Meng Xu wrote:
>> >> 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?
>> >
>> > 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.
>
> Until now what I can tell you is: All Broadwell Server support CAT and some
> models of Haswell Server may also support it.
>
> And the good news is the information @ Intel's website [1] is accurate
> so your purchased "E5-2618L v3" should have it. But you definitely need
> to ask your vendor for the firmware update.

Ah, I didn't do the firmware update and it seems working on Linux with
MSR tools and the CAT tool provided on 01.org.

Now I suspect it is because of some bug in the CAT code of Xen. ;-)

I just sent another email to explain why I think the tool on Linux works. :-P

Thanks,

Meng

-- 


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

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