IB/srp: Reduce number of BUSY conditions
Subsystems (2)
PATCH 3/3 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_SQ_REQ_SIZE - SRP_TSK_MGMT_RSV (62) by reducing the number of BUSY responses reported by ib_srp to the SCSI mid-layer.
Signed-off-by Bart Van Assche <[email protected]>
Cc Roland Dreier <[email protected]>
Cc David Dillow <dave-i1Mk8JYDVaaSihdK6806/[email protected]>
--- drivers/infiniband/ulp/srp/ib_srp.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-)
drivers/infiniband/ulp/srp/ib_srp.c +7 -2
@@ -1354,8 +1354,13 @@ 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); +/* +* Set can_queue such that the SCSI mid-layer +* never causes __srp_get_tx_iu() to fail. +*/ + target->scsi_host->can_queue + =min (target->req_lim -SRP_TSK_MGMT_RSV , + target->scsi_host->can_queue); }else {shost_printk (KERN_WARNING , target->scsi_host,PFX "Unhandled RSP opcode %#x\n" , opcode);
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