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authorDongli Zhang <dongli.zhang@oracle.com>2019-03-27 18:36:34 +0800
committerJens Axboe <axboe@kernel.dk>2019-04-10 08:18:24 -0600
commitbf348f9b78d413e75bb079462751a1d86b6de36c (patch)
treeff62f039df5b908c1c02f8d4074e38ac3b8b9f2a
parenteed47d19d9362bdd958e4ab56af480b9dbf6b2b6 (diff)
virtio-blk: limit number of hw queues by nr_cpu_ids
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. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--drivers/block/virtio_blk.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 4bc083b7c9b5..2a7ca4a1e6f7 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;