Re: [Xen-devel] [PATCH v13 01/23] docs: create Cache Allocation Technology (CAT) and Code and Data Prioritization (CDP) feature document

[Meng Xu <xumengpanda@xxxxxxxxx>]

On Mon, Jul 10, 2017 at 1:25 AM, Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> On 17-07-07 12:37:28, Meng Xu wrote:
>> > +  Sample cache capacity bitmasks for a bitlength of 8 are shown below. 
>> > Please
>> > +  note that all (and only) contiguous '1' combinations are allowed (e.g. 
>> > FFFFH,
>> > +  0FF0H, 003CH, etc.).
>>
>> IIRC, the number of contiguous '1's in CBM should be at least 2 at
>> least on my machine (Intel(R) Xeon(R) CPU E5-2618L v3).
>> I'm unsure if this constraint exist for all CAT-capable processors.
>> For those processors that have such constraint, the system may crash
>> when the user sets only 1 bit to the CBM.
>>
> It seems your machine does not officially support CAT. Per my info, some
> machines, e.g. Haswell, do not officially support CAT but you can enable
> CAT through some actions. On these machines, you may encounter such issue.
>
> Per SDM, we do not have such limitation. Per my test on SKL, 1 bit setting
> works well.

I see.
IIRC, Xen CAT won't be enabled on my haswell machine. As long as all
those machines that does not support 1 bit setting are not enabled by
default, that is fine. Otherwise, this may cause a problem.

>
>>
>> > +      - Member `dom_ids`
>> > +
>> > +        `dom_ids` is a bitmap, every bit corresponds to a domain. Index is
>> > +        domain_id. It is used to help restore domain_id to 0 when a 
>> > socket is
>> > +        offline and then online again.
>>
>> Did you mean "it is used to help restore domain_id to COS0, which has
>> all 1s in CBM, when a socket is offline and then online again."
>>
> Sorry, a typo here, should be:
> "It is used to help restore 'd->arch.psr_cos_ids[socket]' to 0 when a socket 
> is
> offline and then online again."

I think this is more clear.
Another statement could be:
It is used to help restore the cos_id of the domain_id to 0 when a
socket is offline and then online again.

>
> If you think it is still not clear, I may add your explanation:
> ", which has all 1s in CBM, "

If you need to send another version, I think it's better to correct it.

Thanks,

Meng

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

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