Re: [Xen-devel] [PATCH 01/15] xl: update the manpage about "cpus=" and NUMA node-affinity

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-10-03 at 19:45 +0200, Dario Faggioli wrote:
> Since d06b1bf169a01a9c7b0947d7825e58cb455a0ba5 ('libxl: automatic placement
> deals with node-affinity') it is no longer true that, if no "cpus=" option
> is specified, xl picks up some pCPUs by default and pin the domain there.
> 
> In fact, it is the NUMA node-affinity that is affected by automatic
> placement, not vCPU to pCPU pinning.
> 
> Update the xl config file documenation accordingly, as it seems to have
> been forgotten at that time.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

applied since it seems pretty independent.

> ---
> Picking this up from a previously submitted series ("xl:
> allow for node-wise specification of vcpu pinning") as the
> changes in that and in this series would otherwise be
> conflicting. If this is considered fine, Feel free to apply
> it from here and skip the corresponding e-mail in the
> original submission.
> ---
>  docs/man/xl.cfg.pod.5 |   22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
> index d57cd4d..cd96969 100644
> --- a/docs/man/xl.cfg.pod.5
> +++ b/docs/man/xl.cfg.pod.5
> @@ -104,8 +104,8 @@ created online and the remainder will be offline.
>  
>  =item B<cpus="CPU-LIST">
>  
> -List of which cpus the guest is allowed to use. By default xl will pick
> -some cpus on its own (see below). A C<CPU-LIST> may be specified as follows:
> +List of which cpus the guest is allowed to use. Default is no pinning at
> +all (more on this below). A C<CPU-LIST> may be specified as follows:
>  
>  =over 4
>  
> @@ -125,11 +125,19 @@ run on cpu #3 of the host.
>  
>  =back
>  
> -If this option is not specified, libxl automatically tries to place the new
> -domain on the host's NUMA nodes (provided the host has more than one NUMA
> -node) by pinning it to the cpus of those nodes. A heuristic approach is
> -utilized with the goals of maximizing performance for the domain and, at
> -the same time, achieving efficient utilization of the host's CPUs and RAM.
> +If this option is not specified, no vcpu to cpu pinning is established,
> +and the vcpus of the guest can run on all the cpus of the host.
> +
> +If we are on a NUMA machine (i.e., if the host has more than one NUMA
> +node) and this option is not specified, libxl automatically tries to
> +place the guest on the least possible number of nodes. That, however,
> +will not affect vcpu pinning, so the guest will still be able to run on
> +all the cpus, it will just prefer the ones from the node it has been
> +placed on. A heuristic approach is used for choosing the best node (or
> +set of nodes), with the goals of maximizing performance for the guest
> +and, at the same time, achieving efficient utilization of host cpus
> +and memory. See F<docs/misc/xl-numa-placement.markdown> for more
> +details.
>  
>  =back
>  
> 



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