Re: [Xen-devel] [PATCH RFC 7/8] libxl: introduce topology fields

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Feb 22, 2016 at 09:02:13PM +0000, Joao Martins wrote:
> Currently there is "smt" option that changes from a flat core topology
> to a core+thread topology. This patch adds more expressive options for
> describing the topology as seen by the guest i.e. sockets, cores and
> threads to adjust cpu topology as seen by the guest.
> 
> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> ---
> CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  tools/libxl/libxl_dom.c     | 18 ++++++++++++------
>  tools/libxl/libxl_types.idl |  4 ++++
>  2 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
> index ff9356d..1e6d9ab 100644
> --- a/tools/libxl/libxl_dom.c
> +++ b/tools/libxl/libxl_dom.c
> @@ -507,14 +507,20 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
>      }
>  
>      libxl_cpuid_apply_policy(ctx, domid);
> -    if (info->type == LIBXL_DOMAIN_TYPE_HVM
> -        && libxl_defbool_val(info->smt)) {
> +    if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
>  
> -        uint32_t threads = 0;
> +        uint32_t threads = 0, cores = 0;
> +
> +        if (libxl_defbool_val(info->smt)
> +            && !libxl__count_threads_per_core(gc, &threads))
> +            cores = info->max_vcpus / threads;
> +        else if (info->topology.cores) {
> +            cores = info->topology.cores;
> +            threads = info->topology.threads;
> +        }
>  
> -        if (!libxl__count_threads_per_core(gc, &threads))
> -            libxl__cpuid_set_topology(ctx, domid,
> -                                      info->max_vcpus / threads, threads);
> +        if (cores && threads)
> +            libxl__cpuid_set_topology(ctx, domid, cores, threads);
>      }
>  
>      if (info->cpuid != NULL)
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index fa4725a..caba626 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -422,6 +422,10 @@ libxl_domain_build_info = Struct("domain_build_info",[
>      ("vcpu_hard_affinity", Array(libxl_bitmap, "num_vcpu_hard_affinity")),
>      ("vcpu_soft_affinity", Array(libxl_bitmap, "num_vcpu_soft_affinity")),
>      ("smt",             libxl_defbool),
> +    ("topology",        Struct(None, [("sockets", integer),
> +                                      ("cores",   integer),
> +                                      ("threads", integer),
> +                                      ])),

Maybe having topology is a good enough sophisticated configuration
interface? (See my previous email)

Wei.

>      ("numa_placement",  libxl_defbool),
>      ("tsc_mode",        libxl_tsc_mode),
>      ("max_memkb",       MemKB),
> -- 
> 2.1.4
> 

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