Commit 7ade400a authored Aug 30, 2010 by Bart Van Assche Committed by Roland Dreier Oct 24, 2010

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>

parent 05a1d750

drivers/infiniband/ulp/srp/ib_srp.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1339,7 +1339,12 @@ 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,
		/*
		* 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,