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Re: [Xen-devel] [PATCH v3 01/15] docs: L2 Cache Allocation Technology (CAT) feature document.



On Fri, 2016-11-11 at 16:33 -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Oct 25, 2016 at 11:40:49AM +0800, Yi Sun wrote:
> > --- /dev/null
> > +++ b/docs/features/l2_cat.pandoc
> > @@ -0,0 +1,314 @@
> > +% Intel L2 Cache Allocation Technology (L2 CAT) Feature
> > +% Revision 2.0
> > +
> > +\clearpage
> > +
> > +# Basics
> > +
> > +---------------- -----------------------------------------------
> > -----
> > +         Status: **Tech Preview**
> > +
> > +Architecture(s): Intel x86
> > +
> > +   Component(s): Hypervisor, toolstack
> > +
> > +       Hardware: Atom codename Goldmont and beyond
>
Atom codename Goldmont and beyond CPUs

It may sound obvious, but I'd explicitly add that bit.

> > +---------------- -----------------------------------------------
> > -----
> > +
> > +# Overview
> > +
> > +L2 CAT allows an OS or Hypervisor/VMM to control allocation of a
> 
> Could you define CAT?
> 
> > 
> > +CPU's shared L2 cache based on application priority or Class of
> > Service
> > +(COS). Each CLOS is configured using capacity bitmasks (CBM) which
> > +represent cache capacity and indicate the degree of overlap and
> > +isolation between classes. Once L2 CAT is configured, the
> > processor
> > +allows access to portions of L2 cache according to the established
> > +class of service (COS).
> > +
> > +# Technical information
> > +
> > +L2 CAT is a member of Intel PSR features and part of CAT, it
> > shares
> 
> Could you define 'PSR' here? Usually when you introduce an acronym
> you do something like:
> 
> Intel Problem Solver Resolver (PSR)
> 
Wasn't it the 'Intel Probabilistic Silicon Reorganizer' ? :-D :-D

> and that makes it easy for folks to map the acronym to the full
> feature.
> 
Actually, given the density of acronyms, I'd say it would be good to
add a "## Terminology" section at the top, and define all of them there
upfront.

Also, I see that you're meaning this to be committed in tree and act as
the L2 CAT feature document. I know that you've been asked to put it in
tree (although, the request was for docs/misc/) and I think it's good
to have a feature document for L2 CAT.

It contains a lot more technical details than the other (few) feature
documents we have in tree right now. Personally, I'm fine with that,
but I'd say that at least try to filling these sections would be
important:

(from docs/features/template.pandoc)

  # Limitations
  Information concerning incompatibilities with other features or
  hardware combinations.

  # Testing
  Information concerning how to properly test changes affecting this 
  feature.

  # Areas for improvement
  List of enhancements which could be undertaken, e.g. to improve the
  feature itself, or improve interaction with other features.

  # Known issues
  List of known issues or bugs.  For tech preview or experimental
  features, this section must contain the list of items needing fixing
  for its status to be upgraded.

Also, it would be really good to have similar documents for the other
PSR features we have upstream already (perhaps finding a way for not
duplicating all the common information).

Thanks and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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