| Message ID | 1553682995-5682-2-git-send-email-dongli.zhang@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Limit number of hw queues by nr_cpu_ids for virtio-blk and virtio-scsi | expand |
On Wed, Mar 27, 2019 at 06:36:34PM +0800, Dongli Zhang wrote: > When tag_set->nr_maps is 1, the block layer limits the number of hw queues > by nr_cpu_ids. No matter how many hw queues are used by virtio-blk, as it > has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. > > In addition, specifically for pci scenario, when the 'num-queues' specified > by qemu is more than maxcpus, virtio-blk would not be able to allocate more > than maxcpus vectors in order to have a vector for each queue. As a result, > it falls back into MSI-X with one vector for config and one shared for > queues. > > Considering above reasons, this patch limits the number of hw queues used > by virtio-blk by nr_cpu_ids. > > Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> > --- > drivers/block/virtio_blk.c | 2 ++ > 1 file changed, 2 insertions(+) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 4bc083b..b83cb45 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -513,6 +513,8 @@ static int init_vq(struct virtio_blk *vblk) if (err) num_vqs = 1; + num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); + vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL); if (!vblk->vqs) return -ENOMEM;
When tag_set->nr_maps is 1, the block layer limits the number of hw queues by nr_cpu_ids. No matter how many hw queues are used by virtio-blk, as it has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. In addition, specifically for pci scenario, when the 'num-queues' specified by qemu is more than maxcpus, virtio-blk would not be able to allocate more than maxcpus vectors in order to have a vector for each queue. As a result, it falls back into MSI-X with one vector for config and one shared for queues. Considering above reasons, this patch limits the number of hw queues used by virtio-blk by nr_cpu_ids. Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> --- drivers/block/virtio_blk.c | 2 ++ 1 file changed, 2 insertions(+)