Re: [Xen-devel] [RFC 01/16] docs: create Memory Bandwidth Allocation (MBA) feature document.

[Meng Xu <xumengpanda@xxxxxxxxx>]

>> > +  System administrator can change PSR allocation policy at runtime by
>> > +  tool stack. Since MBA shares COS with CAT/CDP, a COS corresponds to a
>> > +  2-tuple, like [CBM, Thrtl] with only-CAT enalbed, when CDP is enable,
>> > +  the COS corresponds to a 3-tuple, like [Code_CBM, Data_CBM, Thrtl]. If
>> > +  neither CAT nor CDP is enabled, things would be easier, one COS
>> > +  corresponds to one Thrtl.
>>
>> How many bits in Thrtl field?
>> Is it decided by the hardware type?
>>
> This is defined in SDM.
> "The definition for the MBA delay value MSRs is provided in Figure 17.39. The
> lower 16 bits are used for MBA delay values, and values from zero to the 
> maximum
> from the CPUID MBA_MAX-1 value are supported."
>
> Please note, MBA value is different with CBM. You do not need care the bits.
>
>> > +# References
>> > +
>> > +"INTEL® RESOURCE DIRECTOR TECHNOLOGY (INTEL® RDT) ALLOCATION FEATURES" 
>> > [Intel® 64 and IA-32 Architectures Software Developer Manuals, 
>> > vol3](http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html)
>> > +
>>
>> I checked the document. The CAT is in Chapter 17.17. However, there is
>> no description about the MBA? ;-)
> Have you downloaded latest SDM? 17.18.7 is for MBA.

Ah-ha, I saw it now. I guess I downloaded the old version. :-)

I found this MBA feature is interesting. Is there any processor on the
market we can purchase?
We'd like to evaluate this feature. ;-)

Thanks,

Meng

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

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