scsi: lpfc: Limit tracking of tgt queue depth in fast path

Performance is affected when target queue depth is tracked.  An atomic
counter is incremented on the submission path which competes with it being
decremented on the completion path.  In addition, multiple CPUs can
simultaniously be manipulating this counter for the same ndlp.

Reduce the overhead by only performing the target increment/decrement when
the target queue depth is less than the overall adapter depth, thus is
actually meaningful.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 44 insertions, 30 deletions

diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index 51ce244cf10a..5c7858e735c9 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/drivers/scsi/lpfc/lpfc_scsi.c
@@ -995,6 +995,11 @@ lpfc_get_scsi_buf_s3(struct lpfc_hba *phba, struct lpfc_nodelist *ndlp)
 		spin_unlock(&phba->scsi_buf_list_put_lock);
 	}
 	spin_unlock_irqrestore(&phba->scsi_buf_list_get_lock, iflag);
+
+	if (lpfc_ndlp_check_qdepth(phba, ndlp) && lpfc_cmd) {
+		atomic_inc(&ndlp->cmd_pending);
+		lpfc_cmd->flags |= LPFC_SBUF_BUMP_QDEPTH;
+	}
 	return  lpfc_cmd;
 }
 /**
@@ -1044,6 +1049,11 @@ lpfc_get_scsi_buf_s4(struct lpfc_hba *phba, struct lpfc_nodelist *ndlp)
 	spin_unlock_irqrestore(&phba->scsi_buf_list_get_lock, iflag);
 	if (!found)
 		return NULL;
+
+	if (lpfc_ndlp_check_qdepth(phba, ndlp) && lpfc_cmd) {
+		atomic_inc(&ndlp->cmd_pending);
+		lpfc_cmd->flags |= LPFC_SBUF_BUMP_QDEPTH;
+	}
 	return  lpfc_cmd;
 }
 /**
@@ -1134,7 +1144,10 @@ lpfc_release_scsi_buf_s4(struct lpfc_hba *phba, struct lpfc_scsi_buf *psb)
 static void
 lpfc_release_scsi_buf(struct lpfc_hba *phba, struct lpfc_scsi_buf *psb)
 {
+	if ((psb->flags & LPFC_SBUF_BUMP_QDEPTH) && psb->ndlp)
+		atomic_dec(&psb->ndlp->cmd_pending);
 
+	psb->flags &= ~LPFC_SBUF_BUMP_QDEPTH;
 	phba->lpfc_release_scsi_buf(phba, psb);
 }
 
@@ -4130,7 +4143,6 @@ lpfc_scsi_cmd_iocb_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pIocbIn,
 		msecs_to_jiffies(vport->cfg_max_scsicmpl_time))) {
 		spin_lock_irqsave(shost->host_lock, flags);
 		if (pnode && NLP_CHK_NODE_ACT(pnode)) {
-			atomic_dec(&pnode->cmd_pending);
 			if (pnode->cmd_qdepth >
 				atomic_read(&pnode->cmd_pending) &&
 				(atomic_read(&pnode->cmd_pending) >
@@ -4143,8 +4155,6 @@ lpfc_scsi_cmd_iocb_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pIocbIn,
 			pnode->last_change_time = jiffies;
 		}
 		spin_unlock_irqrestore(shost->host_lock, flags);
-	} else if (pnode && NLP_CHK_NODE_ACT(pnode)) {
-		atomic_dec(&pnode->cmd_pending);
 	}
 	lpfc_scsi_unprep_dma_buf(phba, lpfc_cmd);
 
@@ -4568,33 +4578,36 @@ lpfc_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *cmnd)
 	 */
 	if (!ndlp || !NLP_CHK_NODE_ACT(ndlp))
 		goto out_tgt_busy;
-	if (atomic_read(&ndlp->cmd_pending) >= ndlp->cmd_qdepth) {
-		lpfc_printf_vlog(vport, KERN_INFO, LOG_FCP_ERROR,
-				 "3377 Target Queue Full, scsi Id:%d Qdepth:%d"
-				 " Pending command:%d"
-				 " WWNN:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x, "
-				 " WWPN:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x",
-				 ndlp->nlp_sid, ndlp->cmd_qdepth,
-				 atomic_read(&ndlp->cmd_pending),
-				 ndlp->nlp_nodename.u.wwn[0],
-				 ndlp->nlp_nodename.u.wwn[1],
-				 ndlp->nlp_nodename.u.wwn[2],
-				 ndlp->nlp_nodename.u.wwn[3],
-				 ndlp->nlp_nodename.u.wwn[4],
-				 ndlp->nlp_nodename.u.wwn[5],
-				 ndlp->nlp_nodename.u.wwn[6],
-				 ndlp->nlp_nodename.u.wwn[7],
-				 ndlp->nlp_portname.u.wwn[0],
-				 ndlp->nlp_portname.u.wwn[1],
-				 ndlp->nlp_portname.u.wwn[2],
-				 ndlp->nlp_portname.u.wwn[3],
-				 ndlp->nlp_portname.u.wwn[4],
-				 ndlp->nlp_portname.u.wwn[5],
-				 ndlp->nlp_portname.u.wwn[6],
-				 ndlp->nlp_portname.u.wwn[7]);
-		goto out_tgt_busy;
+	if (lpfc_ndlp_check_qdepth(phba, ndlp)) {
+		if (atomic_read(&ndlp->cmd_pending) >= ndlp->cmd_qdepth) {
+			lpfc_printf_vlog(vport, KERN_INFO, LOG_FCP_ERROR,
+					 "3377 Target Queue Full, scsi Id:%d "
+					 "Qdepth:%d Pending command:%d"
+					 " WWNN:%02x:%02x:%02x:%02x:"
+					 "%02x:%02x:%02x:%02x, "
+					 " WWPN:%02x:%02x:%02x:%02x:"
+					 "%02x:%02x:%02x:%02x",
+					 ndlp->nlp_sid, ndlp->cmd_qdepth,
+					 atomic_read(&ndlp->cmd_pending),
+					 ndlp->nlp_nodename.u.wwn[0],
+					 ndlp->nlp_nodename.u.wwn[1],
+					 ndlp->nlp_nodename.u.wwn[2],
+					 ndlp->nlp_nodename.u.wwn[3],
+					 ndlp->nlp_nodename.u.wwn[4],
+					 ndlp->nlp_nodename.u.wwn[5],
+					 ndlp->nlp_nodename.u.wwn[6],
+					 ndlp->nlp_nodename.u.wwn[7],
+					 ndlp->nlp_portname.u.wwn[0],
+					 ndlp->nlp_portname.u.wwn[1],
+					 ndlp->nlp_portname.u.wwn[2],
+					 ndlp->nlp_portname.u.wwn[3],
+					 ndlp->nlp_portname.u.wwn[4],
+					 ndlp->nlp_portname.u.wwn[5],
+					 ndlp->nlp_portname.u.wwn[6],
+					 ndlp->nlp_portname.u.wwn[7]);
+			goto out_tgt_busy;
+		}
 	}
-	atomic_inc(&ndlp->cmd_pending);
 
 	lpfc_cmd = lpfc_get_scsi_buf(phba, ndlp);
 	if (lpfc_cmd == NULL) {
@@ -4612,6 +4625,7 @@ lpfc_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *cmnd)
 	 */
 	lpfc_cmd->pCmd  = cmnd;
 	lpfc_cmd->rdata = rdata;
+	lpfc_cmd->ndlp = ndlp;
 	lpfc_cmd->timeout = 0;
 	lpfc_cmd->start_time = jiffies;
 	cmnd->host_scribble = (unsigned char *)lpfc_cmd;
@@ -4694,7 +4708,6 @@ lpfc_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *cmnd)
 	lpfc_scsi_unprep_dma_buf(phba, lpfc_cmd);
 	lpfc_release_scsi_buf(phba, lpfc_cmd);
  out_host_busy:
-	atomic_dec(&ndlp->cmd_pending);
 	return SCSI_MLQUEUE_HOST_BUSY;
 
  out_tgt_busy:
@@ -5047,6 +5060,7 @@ lpfc_send_taskmgmt(struct lpfc_vport *vport, struct scsi_cmnd *cmnd,
 	lpfc_cmd->timeout = phba->cfg_task_mgmt_tmo;
 	lpfc_cmd->rdata = rdata;
 	lpfc_cmd->pCmd = cmnd;
+	lpfc_cmd->ndlp = pnode;
 
 	status = lpfc_scsi_prep_task_mgmt_cmd(vport, lpfc_cmd, lun_id,
 					   task_mgmt_cmd);