scsi: lpfc: Separate CQ processing for nvmet_fc upcalls

Currently the driver is notified of new command frame receipt by CQEs. As
part of the CQE processing, the driver upcalls the nvmet_fc transport to
deliver the command. nvmet_fc, as part of receiving the command builds out
a context for it, where one of the first steps is to allocate memory for
the io.

When running with tests that do large ios (1MB), it was found on some
systems, the total number of outstanding I/O's, at 1MB per, completely
consumed the system's memory. Thus additional ios were getting blocked in
the memory allocator.  Given that this blocked the lpfc thread processing
CQEs, there were lots of other commands that were received and which are
then held up, and given CQEs are serially processed, the aggregate delays
for an IO waiting behind the others became cummulative - enough so that the
initiator hit timeouts for the ios.

The basic fix is to avoid the direct upcall and instead schedule a work
item for each io as it is received. This allows the cq processing to
complete very quickly, and each io can then run or block on it's own.
However, this general solution hurts latency when there are few ios.  As
such, implemented the fix such that the driver watches how many CQEs it has
processed sequentially in one run. As long as the count is below a
threshold, the direct nvmet_fc upcall will be made. Only when the count is
exceeded will it revert to work scheduling.

Given that debug of this showed a surprisingly long delay in cq processing,
the io timer stats were updated to better reflect the processing of the
different points.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 47 insertions, 20 deletions

diff --git a/drivers/scsi/lpfc/lpfc_nvmet.c b/drivers/scsi/lpfc/lpfc_nvmet.c
index 3a11861b7ad6..95386f90a874 100644
--- a/drivers/scsi/lpfc/lpfc_nvmet.c
+++ b/drivers/scsi/lpfc/lpfc_nvmet.c
@@ -395,8 +395,9 @@ lpfc_nvmet_ctxbuf_post(struct lpfc_hba *phba, struct lpfc_nvmet_ctxbuf *ctx_buf)
 		spin_lock_init(&ctxp->ctxlock);
 
 #ifdef CONFIG_SCSI_LPFC_DEBUG_FS
-		if (ctxp->ts_cmd_nvme) {
-			ctxp->ts_cmd_nvme = ktime_get_ns();
+		/* NOTE: isr time stamp is stale when context is re-assigned*/
+		if (ctxp->ts_isr_cmd) {
+			ctxp->ts_cmd_nvme = 0;
 			ctxp->ts_nvme_data = 0;
 			ctxp->ts_data_wqput = 0;
 			ctxp->ts_isr_data = 0;
@@ -1877,6 +1878,10 @@ lpfc_nvmet_process_rcv_fcp_req(struct lpfc_nvmet_ctxbuf *ctx_buf)
 
 	payload = (uint32_t *)(nvmebuf->dbuf.virt);
 	tgtp = (struct lpfc_nvmet_tgtport *)phba->targetport->private;
+#ifdef CONFIG_SCSI_LPFC_DEBUG_FS
+	if (ctxp->ts_isr_cmd)
+		ctxp->ts_cmd_nvme = ktime_get_ns();
+#endif
 	/*
 	 * The calling sequence should be:
 	 * nvmet_fc_rcv_fcp_req->lpfc_nvmet_xmt_fcp_op/cmp- req->done
@@ -2015,6 +2020,8 @@ lpfc_nvmet_replenish_context(struct lpfc_hba *phba,
  * @phba: pointer to lpfc hba data structure.
  * @idx: relative index of MRQ vector
  * @nvmebuf: pointer to lpfc nvme command HBQ data structure.
+ * @isr_timestamp: in jiffies.
+ * @cqflag: cq processing information regarding workload.
  *
  * This routine is used for processing the WQE associated with a unsolicited
  * event. It first determines whether there is an existing ndlp that matches
@@ -2027,7 +2034,8 @@ static void
 lpfc_nvmet_unsol_fcp_buffer(struct lpfc_hba *phba,
 			    uint32_t idx,
 			    struct rqb_dmabuf *nvmebuf,
-			    uint64_t isr_timestamp)
+			    uint64_t isr_timestamp,
+			    uint8_t cqflag)
 {
 	struct lpfc_nvmet_rcv_ctx *ctxp;
 	struct lpfc_nvmet_tgtport *tgtp;
@@ -2136,24 +2144,41 @@ lpfc_nvmet_unsol_fcp_buffer(struct lpfc_hba *phba,
 	spin_lock_init(&ctxp->ctxlock);
 
 #ifdef CONFIG_SCSI_LPFC_DEBUG_FS
-	if (isr_timestamp) {
+	if (isr_timestamp)
 		ctxp->ts_isr_cmd = isr_timestamp;
-		ctxp->ts_cmd_nvme = ktime_get_ns();
-		ctxp->ts_nvme_data = 0;
-		ctxp->ts_data_wqput = 0;
-		ctxp->ts_isr_data = 0;
-		ctxp->ts_data_nvme = 0;
-		ctxp->ts_nvme_status = 0;
-		ctxp->ts_status_wqput = 0;
-		ctxp->ts_isr_status = 0;
-		ctxp->ts_status_nvme = 0;
-	} else {
-		ctxp->ts_cmd_nvme = 0;
-	}
+	ctxp->ts_cmd_nvme = 0;
+	ctxp->ts_nvme_data = 0;
+	ctxp->ts_data_wqput = 0;
+	ctxp->ts_isr_data = 0;
+	ctxp->ts_data_nvme = 0;
+	ctxp->ts_nvme_status = 0;
+	ctxp->ts_status_wqput = 0;
+	ctxp->ts_isr_status = 0;
+	ctxp->ts_status_nvme = 0;
 #endif
 
 	atomic_inc(&tgtp->rcv_fcp_cmd_in);
-	lpfc_nvmet_process_rcv_fcp_req(ctx_buf);
+	/* check for cq processing load */
+	if (!cqflag) {
+		lpfc_nvmet_process_rcv_fcp_req(ctx_buf);
+		return;
+	}
+
+	if (!queue_work(phba->wq, &ctx_buf->defer_work)) {
+		atomic_inc(&tgtp->rcv_fcp_cmd_drop);
+		lpfc_printf_log(phba, KERN_ERR, LOG_NVME,
+				"6325 Unable to queue work for oxid x%x. "
+				"FCP Drop IO [x%x x%x x%x]\n",
+				ctxp->oxid,
+				atomic_read(&tgtp->rcv_fcp_cmd_in),
+				atomic_read(&tgtp->rcv_fcp_cmd_out),
+				atomic_read(&tgtp->xmt_fcp_release));
+
+		spin_lock_irqsave(&ctxp->ctxlock, iflag);
+		lpfc_nvmet_defer_release(phba, ctxp);
+		spin_unlock_irqrestore(&ctxp->ctxlock, iflag);
+		lpfc_nvmet_unsol_fcp_issue_abort(phba, ctxp, sid, oxid);
+	}
 }
 
 /**
@@ -2190,6 +2215,8 @@ lpfc_nvmet_unsol_ls_event(struct lpfc_hba *phba, struct lpfc_sli_ring *pring,
  * @phba: pointer to lpfc hba data structure.
  * @idx: relative index of MRQ vector
  * @nvmebuf: pointer to received nvme data structure.
+ * @isr_timestamp: in jiffies.
+ * @cqflag: cq processing information regarding workload.
  *
  * This routine is used to process an unsolicited event received from a SLI
  * (Service Level Interface) ring. The actual processing of the data buffer
@@ -2201,14 +2228,14 @@ void
 lpfc_nvmet_unsol_fcp_event(struct lpfc_hba *phba,
 			   uint32_t idx,
 			   struct rqb_dmabuf *nvmebuf,
-			   uint64_t isr_timestamp)
+			   uint64_t isr_timestamp,
+			   uint8_t cqflag)
 {
 	if (phba->nvmet_support == 0) {
 		lpfc_rq_buf_free(phba, &nvmebuf->hbuf);
 		return;
 	}
-	lpfc_nvmet_unsol_fcp_buffer(phba, idx, nvmebuf,
-				    isr_timestamp);
+	lpfc_nvmet_unsol_fcp_buffer(phba, idx, nvmebuf, isr_timestamp, cqflag);
 }
 
 /**