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virtio-scsi-pci: default num_queues to -smp N

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Automatically size the number of virtio-scsi-pci, vhost-scsi-pci, and
vhost-user-scsi-pci request virtqueues to match the number of vCPUs.
Other transports continue to default to 1 request virtqueue.

A 1:1 virtqueue:vCPU mapping ensures that completion interrupts are
handled on the same vCPU that submitted the request.  No IPI is
necessary to complete an I/O request and performance is improved.  The
maximum number of MSI-X vectors and virtqueues limit are respected.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200818143348.310613-6-stefanha@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-08-18 15:33:46 +01:00 • committed by Michael S. Tsirkin
parent 4e5163bd84
commit 6a55882284
8 changed files with 37 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

10
hw/virtio/virtio-scsi-pci.c
View file

@ -46,13 +46,17 @@ static void virtio_scsi_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
{
VirtIOSCSIPCI *dev = VIRTIO_SCSI_PCI(vpci_dev);
DeviceState *vdev = DEVICE(&dev->vdev);
VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
DeviceState *proxy = DEVICE(vpci_dev);
VirtIOSCSIConf *conf = &dev->vdev.parent_obj.conf;
char *bus_name;
if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
conf->num_queues =
virtio_pci_optimal_num_queues(VIRTIO_SCSI_VQ_NUM_FIXED);
}
if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
vpci_dev->nvectors = vs->conf.num_queues +
VIRTIO_SCSI_VQ_NUM_FIXED + 1;
vpci_dev->nvectors = conf->num_queues + VIRTIO_SCSI_VQ_NUM_FIXED + 1;
}
/*