netdev-dpdk: Delay vhost mempool creation.

Currently mempools for vhost are being assigned before the vhost device
is added.  In some cases this may be just reusing an existing mempool but
in others it can require creation of a mempool.

For multi-NUMA, the NUMA info of the vhost port is not known until a
device is added to the port, so on multi-NUMA systems the initial NUMA
node for the mempool is a best guess based on vswitchd affinity.

When a device is added to the vhost port, the NUMA info can be checked
and if the guess was incorrect a mempool on the correct NUMA node
created.

For multi-NUMA, the current scheme can have the effect of creating a
mempool on a NUMA node that will not be needed and at least for a certain
time period requires more memory on a NUMA node.

It is also difficult for a user trying to provision memory on different
NUMA nodes, if they are not sure which NUMA node the initial mempool
for a vhost port will be on.

For single NUMA, even though the mempool will be on the correct NUMA, it
is assigned ahead of time and if a vhost device was not added, it could
also be using uneeded memory.

This patch delays the creation of the mempool for a vhost port until the
vhost device is added.

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 994fdf6a9..69f5f4355 100644
--- a/NEWS
+++ b/NEWS
@@ -39,6 +39,9 @@ Post-v2.17.0
    - DPDK:
      * OVS validated with DPDK 21.11.1.  It is recommended to use this version
        until further releases.
+     * Delay creating or reusing a mempool for vhost ports until the VM
+       is started. A failure to create a mempool will now be logged only
+       when the VM is started.
    - Userspace datapath:
      * 'dpif-netdev/subtable-lookup-prio-get' appctl command renamed to
        'dpif-netdev/subtable-lookup-info-get' to better reflect its purpose.