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

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

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.

> 
> > 
> > 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.

> > +
> > +#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.

> 
> > +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.

> 
> > @@ -247,6 +290,75 @@ out:
> >      return rc;
> >  }
> >  
> > +int libxl_psr_cat_set_cbm(libxl_ctx *ctx, uint32_t domid,
> > +                          libxl_psr_cat_type type, uint32_t target,
> > +                          uint64_t cbm)
> > +{
> > +    GC_INIT(ctx);
> > +    int rc;
> > +
> > +    uint32_t i, nr_sockets;
> > +
> > +    if (target != LIBXL_PSR_TARGET_ALL) {
> > +        rc = xc_psr_cat_set_domain_data(ctx->xch, domid, type, target, 
> > cbm);
> > +        if (rc < 0) {
> > +            libxl__psr_cat_log_err_msg(gc, errno);
> > +            rc = ERROR_FAIL;
> > +        }
> > +    } else {
> > +        nr_sockets = libxl_count_physical_sockets(ctx);
> > +        if (nr_sockets == 0) {
> > +            LOGE(ERROR, "failed to get system socket count");
> > +            rc = ERROR_FAIL;
> > +            goto out;
> > +        }
> > +        for (i = 0; i < nr_sockets; i++) {
> > +            rc = xc_psr_cat_set_domain_data(ctx->xch, domid, type, i, cbm);
> > +            if (rc < 0) {
> > +                libxl__psr_cat_log_err_msg(gc, errno);
> > +                rc = ERROR_FAIL;
> 
> You neither error out nor latch this value, so you only return the
> status of the final socket.
> 
> I think you probably want to exit on first error. And depending on the
> semantics of this stuff you may also need to unwind any work already
> done.

That's right, exit on first error is my initial purpose. 

> 
> > diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> > index f26a02d..ff963df 100644
> > --- a/tools/libxl/xl_cmdimpl.c
> > +++ b/tools/libxl/xl_cmdimpl.c
> > @@ -8038,6 +8038,152 @@ int main_psr_cmt_show(int argc, char **argv)
> >  }
> >  #endif
> >  
> > +#ifdef LIBXL_HAVE_PSR_CAT
> > +static void psr_cat_print_one_domain_cbm(libxl_dominfo *dominfo,
> > +                                         uint32_t socket)
> > +{
> > +    char *domain_name;
> > +    uint64_t cbm;
> > +
> > +    domain_name = libxl_domid_to_name(ctx, dominfo->domid);
> 
> AFAICT you use dominfo here for domifo->domid, but you looked it up with
> libxl_domain_info(,... domid) so you already had that in your hand.
> 
> IOW I think you can just pass the domid to this function, and omit the
> call to libxl_domain_info in the callers, or use list->domid in the case
> you have that in hand.

Agreed.

> 
> > +    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.

Chao

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