From: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Date: Fri, 25 Nov 2016 06:43:08 +0200 > On Fri, Nov 25, 2016 at 12:37:26PM +0800, Jason Wang wrote: >> We use single queue even if multiqueue is enabled and let admin to >> enable it through ethtool later. This is used to avoid possible >> regression (small packet TCP stream transmission). But looks like an >> overkill since: >> >> - single queue user can disable multiqueue when launching qemu >> - brings extra troubles for the management since it needs extra admin >> tool in guest to enable multiqueue >> - multiqueue performs much better than single queue in most of the >> cases >> >> So this patch enables multiqueue by default: if #queues is less than or >> equal to #vcpu, enable as much as queue pairs; if #queues is greater >> than #vcpu, enable #vcpu queue pairs. >> >> Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxx> >> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx> >> Cc: Neil Horman <nhorman@xxxxxxxxxx> >> Cc: Jeremy Eder <jeder@xxxxxxxxxx> >> Cc: Marko Myllynen <myllynen@xxxxxxxxxx> >> Cc: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx> >> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx> > > OK at some level but all uses of num_online_cpus() > like this are racy versus hotplug. > I know we already have this bug but shouldn't we fix it > before we add more? This is more being used like a heuristic in this scenerio, and in fact I would say one would keep the code this way even once proper hotplug handlers are installed to adjust the queued dynamically if there is a desired (which is also not necessarily the case). I really don't think this change should be held on up on this issue. So can we please make some forward progress here? Thanks. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
