On Mon, 9 Nov 2020 17:06:16 +0100 Cornelia Huck <coh...@redhat.com> wrote:
> > @@ -20,6 +21,11 @@ static void virtio_ccw_blk_realize(VirtioCcwDevice > > *ccw_dev, Error **errp) > > { > > VirtIOBlkCcw *dev = VIRTIO_BLK_CCW(ccw_dev); > > DeviceState *vdev = DEVICE(&dev->vdev); > > + VirtIOBlkConf *conf = &dev->vdev.conf; > > + > > + if (conf->num_queues == VIRTIO_BLK_AUTO_NUM_QUEUES) { > > + conf->num_queues = MIN(4, current_machine->smp.cpus); > > + } > > I would like to have a comment explaining the numbers here, however. > > virtio-pci has a pretty good explanation (use 1:1 for vqs:vcpus if > possible, apply some other capping). 4 seems to be a bit arbitrary > without explanation, although I'm sure you did some measurements :) Frankly, I don't have any measurements yet. For the secure case, I think Mimu has assessed the impact of multiqueue, hence adding Mimu to the cc list. @Mimu can you help us out. Regarding the normal non-protected VMs I'm in a middle of producing some measurement data. This was admittedly a bit rushed because of where we are in the cycle. Sorry to disappoint you. The number 4 was suggested by Christian, maybe Christian does have some readily available measurement data for the normal VM case. @Christian: can you help me out? Regards, Halil