On 12/2/20 11:27 AM, Tyrel Datwyler wrote:

On 12/2/20 7:14 AM, Brian King wrote:

quoted

On 12/1/20 6:53 PM, Tyrel Datwyler wrote:

quoted

Introduce several new vhost fields for managing MQ state of the adapter
as well as initial defaults for MQ enablement.

Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
---
 drivers/scsi/ibmvscsi/ibmvfc.c |  9 ++++++++-
 drivers/scsi/ibmvscsi/ibmvfc.h | 13 +++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index 42e4d35e0d35..f1d677a7423d 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c

@@ -5161,12 +5161,13 @@ static int ibmvfc_probe(struct vio_dev *vdev, const struct vio_device_id *id)
 	}
 
 	shost->transportt = ibmvfc_transport_template;
-	shost->can_queue = max_requests;
+	shost->can_queue = (max_requests / IBMVFC_SCSI_HW_QUEUES);

This doesn't look right. can_queue is the SCSI host queue depth, not the MQ queue depth.

Our max_requests is the total number commands allowed across all queues. From
what I understand is can_queue is the total number of commands in flight allowed
for each hw queue.

        /*
         * In scsi-mq mode, the number of hardware queues supported by the LLD.
         *
         * Note: it is assumed that each hardware queue has a queue depth of
         * can_queue. In other words, the total queue depth per host
         * is nr_hw_queues * can_queue. However, for when host_tagset is set,
         * the total queue depth is can_queue.
         */

We currently don't use the host wide shared tagset.

Ok. I missed that bit... In that case, since we allocate by default only 100
event structs. If we slice that across IBMVFC_SCSI_HW_QUEUES (16) queues, then
we end up with only about 6 commands that can be outstanding per queue,
which is going to really hurt performance... I'd suggest bumping up
IBMVFC_MAX_REQUESTS_DEFAULT from 100 to 1000 as a starting point.

Thanks,

Brian


-- 
Brian King
Power Linux I/O
IBM Linux Technology Center