On Sat, Aug 1, 2026 at 2:21 AM Liu, Changcheng <[email protected]> wrote: > > When creating many virtio-blk devices, probe starts failing with > -ENOSPC (-28) because the system runs out of interrupt vectors: > > virtio_blk virtioNNN: probe with driver virtio_blk failed with error -28 > > By default virtio-blk uses managed IRQ affinity, which reserves an > interrupt vector on every CPU for each device (about nr_cpus vectors per > device). On a host with many CPUs and many devices this exhausts the > vectors long before all devices are probed. > > Add use_irq_affinity (default true, no behaviour change). Set it to 0 to > use unmanaged interrupts, so each device only uses a couple of vectors > instead of one per CPU, allowing far more devices to probe. > > Signed-off-by: Liu, Changcheng <[email protected]>
There is already a num_request_queues module parameter for cases where the user wishes to reduce the number of virtqueues. Did you benchmark that and decide the performance of many queues sharing a single irq makes it worth adding another module parameter? Stefan > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 32bf3ba07a9d..184f1c1f4485 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -41,6 +41,11 @@ static unsigned int poll_queues; > module_param(poll_queues, uint, 0644); > MODULE_PARM_DESC(poll_queues, "The number of dedicated virtqueues for > polling I/O"); > > +static bool use_irq_affinity = true; > +module_param(use_irq_affinity, bool, 0644); > +MODULE_PARM_DESC(use_irq_affinity, > + "Use managed IRQ affinity for virtqueues (default: true)"); > + > static int major; > static DEFINE_IDA(vd_index_ida); > > @@ -1016,7 +1021,8 @@ static int init_vq(struct virtio_blk *vblk) > } > > /* Discover virtqueues and write information to configuration. */ > - err = virtio_find_vqs(vdev, num_vqs, vqs, vqs_info, &desc); > + err = virtio_find_vqs(vdev, num_vqs, vqs, vqs_info, > + use_irq_affinity ? &desc : NULL); > if (err) > goto out; > > -- > 2.43.7 > >
