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envelope-from=pasic@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/09 13:53:43 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , "Michael S. Tsirkin" , David Hildenbrand , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Michael Mueller Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 9 Nov 2020 17:06:16 +0100 Cornelia Huck 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