Re: [Xen-devel] [PATCH v3 8/8] tools: add tools support for Intel CAT

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

On Wed, Apr 01, 2015 at 09:41:06AM +0100, Ian Campbell wrote:
> On Wed, 2015-04-01 at 15:55 +0800, Chao Peng wrote:
> > On Tue, Mar 31, 2015 at 05:28:54PM +0100, Ian Campbell wrote:
> > > On Thu, 2015-03-26 at 20:38 +0800, Chao Peng wrote:
> > > > This is the xc/xl changes to support Intel Cache Allocation
> > > > Technology(CAT). Two commands are introduced:
> > > > - xl psr-cat-cbm-set [-s socket] <domain> <cbm>
> > > >   Set cache capacity bitmasks(CBM) for a domain.
> > > > - xl psr-cat-show <domain>
> > > >   Show Cache Allocation Technology information.
> > > 
> > > Please could you show an example of the output from this one.
> > 
> > I did put the sample output in the cover letter, but sounds like here is
> > the right place.
> 
> Sorry, I didn't think to look there at the time.
> 
> > > 
> > > > 
> > > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > > > ---
> > > > +
> > > > +=item B<psr-cat-cbm-set> [I<OPTIONS>] [I<domain-id>]
> > > > +
> > > > +Set cache capacity bitmasks(CBM) for a domain.
> > > 
> > > What is the syntax of these bitmaps, and where do I pass them?
> > 
> > [I<cbm>] is missing here.
> > 
> > > 
> > > I think there is also a bunch of terminology (CBM, COS) which need
> > > explaining, otherwise no one will know how to use it. Perhaps that
> > > belongs in a separate document or the wiki though?
> > 
> > Sounds it's worthy to create docs/misc/xl-psr.markdown.
> 
> I think the syntax of I<cbm> needs to be in this document, for sure, but
> I suspect that this stuff is complex enough that a more complete
> overview in a separate document might be useful too (possibly it should
> cover other related things, like the existing stuff like CMT and MBM
> too, assuming they are related enough?

Yes, they are also in the plan.

> 
> > 
> > > > +
> > > > +#define LIBXL_PSR_TARGET_ALL (~0U)
> > > > +int libxl_psr_cat_set_cbm(libxl_ctx *ctx, uint32_t domid,
> > > > +                          libxl_psr_cat_type type, uint32_t target,
> > > > +                          uint64_t cbm);
> > > > +int libxl_psr_cat_get_cbm(libxl_ctx *ctx, uint32_t domid,
> > > > +                          libxl_psr_cat_type type, uint32_t target,
> > > > +                          uint64_t *cbm_r);
> > > 
> > > What are the units of the various cbm*
> 
> ?
> 
> > > 
> > > If they are now more precisely typed (i.e. not the opaque data from last
> > > time) then is the type parameter still needed?
> > 
> > 'type' is still used because in the future the possible value can be
> > L3_CODE_CBM/L3_DATA_CBM or even L2_CBM. We want to keep it common.
> 
> OK. And all future "cat_type" values will all have similar
> types/semantics?

Yes, they will. 

> 
> > > > +int libxl_psr_cat_get_l3_info(libxl_ctx *ctx, uint32_t socket,
> > > > +                              uint32_t *cos_max_r, uint32_t 
> > > > *cbm_len_r);
> > > 
> > > Is there going to be any user documentation regarding what cos and cbm
> > > are and how to interpret them and set them?
> > 
> > So I'd like to create docs/misc/xl-psr.markdown to answer all these
> > questions.
> 
> OK.
> 
> 
> > > 
> > > > +    printf("%5d%25s", dominfo->domid, domain_name);
> > > > +    free(domain_name);
> > > > +
> > > > +    if (!libxl_psr_cat_get_cbm(ctx, dominfo->domid,
> > > > +                               LIBXL_PSR_CAT_TYPE_L3_CBM, socket, 
> > > > &cbm))
> > > > +         printf("%#16"PRIx64, cbm);
> > > > +
> > > > +    printf("\n");
> > > > +}
> > > > +
> > > > +static int psr_cat_print_socket(uint32_t domid, uint32_t socket)
> > > > +{
> > > > +    uint32_t l3_cache_size, cos_max, cbm_len;
> > > > +    int rc;
> > > > +
> > > > +    rc = libxl_psr_cmt_get_l3_cache_size(ctx, socket, &l3_cache_size);
> > > > +    if (rc) {
> > > > +        fprintf(stderr, "Failed to get l3 cache size for socket:%d\n", 
> > > > socket);
> > > > +        return -1;
> > > > +    }
> > > > +
> > > > +    rc = libxl_psr_cat_get_l3_info(ctx, socket, &cos_max, &cbm_len);
> > > 
> > > Would an interface which returns a list with information for all sockets
> > > not be more convenient?
> > 
> > If this one returns all sockets but not a specified socket data (which I 
> > agreed)
> > and not consider legacy cmt code, then I think I can make
> > libxl_count_physical_sockets() private and move it to libxl/libxl_psr.c.
> 
> What is the legacy cmt code? But otherwise I agree, yes.

In libxl/xl_cmdimpl.c, psr_cmt_show also calculates the socket count
itself. If we want to refactor it with new libxl_count_physical_sockets
then libxl_count_physical_sockets should be public, otherwise it can be
private to libxl_psr.c only. From my side, both directions sound OK.

Chao

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