From 7ade400aba9a675b610074d6609658661db07eeb Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Mon, 30 Aug 2010 19:27:36 +0000 Subject: 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 Signed-off-by: David Dillow Signed-off-by: Roland Dreier --- drivers/infiniband/ulp/srp/ib_srp.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'drivers') 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); -- cgit v1.2.3