From e174e07bb45346385f3eed89deebce25f42f450e Mon Sep 17 00:00:00 2001 From: Dario Faggioli Date: Thu, 3 Oct 2013 19:45:38 +0200 Subject: 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 Acked-by: Ian Jackson --- docs/man/xl.cfg.pod.5 | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) (limited to 'docs') 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 -List of which cpus the guest is allowed to use. By default xl will pick -some cpus on its own (see below). A C 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 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 for more +details. =back -- cgit v1.2.3