From: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Date: Fri, 5 Jan 2018 05:27:45 -0800
Subject: [PATCH] scsi: megaraid_sas: Selectively apply stream detection based
 on IO type
References: bsc#1077408
Git-commit: 4959e61b83a3bc53d49b023dcb4dc50150c2795e
Patch-mainline: v4.16-rc1

Performance improvement:

Current driver calls stream detection unconditionally for all IOs.
Stream Detection logic is not required for most of the fast path IO. To
improve performance, avoid stream detection logic and do it only if
required.

Below are the cases where stream detection is required in driver:

1. All non-FastPath IOs (IOs going to FW)
2. Fast Path reads sent to ReadAhead capable VDs.

Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/megaraid/megaraid_sas_fusion.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 74dadd052be4..ef36f2ac7cb6 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -2664,16 +2664,6 @@ megasas_build_ldio_fusion(struct megasas_instance *instance,
 	praid_context = &io_request->RaidContext;
 
 	if (instance->adapter_type == VENTURA_SERIES) {
-		spin_lock_irqsave(&instance->stream_lock, spinlock_flags);
-		megasas_stream_detect(instance, cmd, &io_info);
-		spin_unlock_irqrestore(&instance->stream_lock, spinlock_flags);
-		/* In ventura if stream detected for a read and it is read ahead
-		 *  capable make this IO as LDIO
-		 */
-		if (is_stream_detected(&io_request->RaidContext.raid_context_g35) &&
-		    io_info.isRead && io_info.ra_capable)
-			fp_possible = false;
-
 		/* FP for Optimal raid level 1.
 		 * All large RAID-1 writes (> 32 KiB, both WT and WB modes)
 		 * are built by the driver as LD I/Os.
@@ -2699,6 +2689,20 @@ megasas_build_ldio_fusion(struct megasas_instance *instance,
 			}
 		}
 
+		if (!fp_possible ||
+		    (io_info.isRead && io_info.ra_capable)) {
+			spin_lock_irqsave(&instance->stream_lock,
+					  spinlock_flags);
+			megasas_stream_detect(instance, cmd, &io_info);
+			spin_unlock_irqrestore(&instance->stream_lock,
+					       spinlock_flags);
+			/* In ventura if stream detected for a read and it is
+			 * read ahead capable make this IO as LDIO
+			 */
+			if (is_stream_detected(&io_request->RaidContext.raid_context_g35))
+				fp_possible = false;
+		}
+
 		/* If raid is NULL, set CPU affinity to default CPU0 */
 		if (raid)
 			megasas_set_raidflag_cpu_affinity(praid_context,
-- 
2.12.3