From: Bart Van Assche <bvanass...@acm.org>
As proposed by the SRP (draft) standard, ib_srp reserves one ring
element for SRP_TSK_MGMT requests. This patch makes sure that the SCSI
mid-layer never tries to queue more than (SRP request limit) - 1 SCSI
commands to ib_srp. This improves performance for targets whose request
limit is less than or equal to SRP_NORMAL_REQ_SQ_SIZE by reducing the
number of BUSY responses reported by ib_srp to the SCSI mid-layer.
Signed-off-by: Bart Van Assche <bvanass...@acm.org>
Signed-off-by: David Dillow <dillo...@ornl.gov>
---
drivers/infiniband/ulp/srp/ib_srp.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c
b/drivers/infiniband/ulp/srp/ib_srp.c
index d4c08d6..4df8275 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1339,8 +1339,13 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct
ib_cm_event *event)
target->max_ti_iu_len = be32_to_cpu(rsp->max_ti_iu_len);
target->req_lim = be32_to_cpu(rsp->req_lim_delta);
- target->scsi_host->can_queue = min(target->req_lim,
-
target->scsi_host->can_queue);
+ /*
+ * Reserve credits for task management so we don't
+ * bounce requests back to the SCSI mid-layer.
+ */
+ target->scsi_host->can_queue
+ = min(target->req_lim - SRP_TSK_MGMT_SQ_SIZE,
+ target->scsi_host->can_queue);
} else {
shost_printk(KERN_WARNING, target->scsi_host,
PFX "Unhandled RSP opcode %#x\n", opcode);
--
1.7.2.3
--
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