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authorBart Van Assche <bvanassche@acm.org>2010-08-30 19:27:36 +0000
committerRoland Dreier <rolandd@cisco.com>2010-10-24 22:14:14 -0700
commit7ade400aba9a675b610074d6609658661db07eeb (patch)
tree609a1370a1a8d416c789905c17607bd8d31c6242
parent05a1d7504f836ee67e27f2488cb5b8126b51dbd4 (diff)
IB/srp: Reduce number of BUSY conditions
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 <bvanassche@acm.org> Signed-off-by: David Dillow <dillowda@ornl.gov> Signed-off-by: Roland Dreier <rolandd@cisco.com>
-rw-r--r--drivers/infiniband/ulp/srp/ib_srp.c9
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 d4c08d648137..4df827591cad 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);