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| author | Dongli Zhang <dongli.zhang@oracle.com> | 2019-03-27 13:36:35 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-04-10 17:18:25 +0300 |
| commit | 1978f30a87732d4d9072a20abeded9fe17884f1b (patch) | |
| tree | df4d83ad5a1996234900cc4424f413d978eec139 /drivers/scsi/virtio_scsi.c | |
| parent | bf348f9b78d413e75bb079462751a1d86b6de36c (diff) | |
| download | linux-1978f30a87732d4d9072a20abeded9fe17884f1b.tar.xz | |
scsi: virtio_scsi: 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-scsi, 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-scsi 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-scsi 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>
Diffstat (limited to 'drivers/scsi/virtio_scsi.c')
| -rw-r--r-- | drivers/scsi/virtio_scsi.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c index 8af01777d09c..f8cb7c23305b 100644 --- a/drivers/scsi/virtio_scsi.c +++ b/drivers/scsi/virtio_scsi.c @@ -793,6 +793,7 @@ static int virtscsi_probe(struct virtio_device *vdev) /* We need to know how many queues before we allocate. */ num_queues = virtscsi_config_get(vdev, num_queues) ? : 1; + num_queues = min_t(unsigned int, nr_cpu_ids, num_queues); num_targets = virtscsi_config_get(vdev, max_target) + 1; |