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| author | Dario Faggioli <dario.faggioli@citrix.com> | 2013-10-03 19:45:38 +0200 |
|---|---|---|
| committer | Ian Campbell <ian.campbell@citrix.com> | 2013-10-10 12:28:56 +0100 |
| commit | e174e07bb45346385f3eed89deebce25f42f450e (patch) | |
| tree | eef7a65cc66eb414cd48893bf5b707949d6cf74f | |
| parent | 7051d5c872e3e708b2d4b2088215d6ab1b33de1b (diff) | |
| download | xen-e174e07bb45346385f3eed89deebce25f42f450e.tar.gz xen-e174e07bb45346385f3eed89deebce25f42f450e.tar.bz2 xen-e174e07bb45346385f3eed89deebce25f42f450e.zip | |
xl: update the manpage about "cpus=" and NUMA node-affinity
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@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
| -rw-r--r-- | docs/man/xl.cfg.pod.5 | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5 index d57cd4dfd9..cd9696934b 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 |