linux-kernel - [PATCH 4.4 06/30] cxlflash: Increase cmd_per

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Date:   Fri, 24 Mar 2017 18:58:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Manoj N. Kumar" <manoj@...ux.vnet.ibm.com>,
        "Matthew R. Ochs" <mrochs@...ux.vnet.ibm.com>,
        Uma Krishnan <ukrishn@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: [PATCH 4.4 06/30] cxlflash: Increase cmd_per_lun for better throughput

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Manoj N. Kumar <manoj@...ux.vnet.ibm.com>

commit 83430833b4d4a9c9b23964babbeb1f36450f8136 upstream.

With the current value of cmd_per_lun at 16, the throughput
over a single adapter is limited to around 150kIOPS.

Increase the value of cmd_per_lun to 256 to improve
throughput. With this change a single adapter is able to
attain close to the maximum throughput (380kIOPS).
Also change the number of RRQ entries that can be queued.

Signed-off-by: Manoj N. Kumar <manoj@...ux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@...ux.vnet.ibm.com>
Reviewed-by: Uma Krishnan <ukrishn@...ux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/scsi/cxlflash/common.h |    8 +++++---
 drivers/scsi/cxlflash/main.c   |    2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/scsi/cxlflash/common.h
+++ b/drivers/scsi/cxlflash/common.h
@@ -34,7 +34,6 @@ extern const struct file_operations cxlf
 								   sectors
 								*/
 
-#define NUM_RRQ_ENTRY    16     /* for master issued cmds */
 #define MAX_RHT_PER_CONTEXT (PAGE_SIZE / sizeof(struct sisl_rht_entry))
 
 /* AFU command retry limit */
@@ -48,9 +47,12 @@ extern const struct file_operations cxlf
 							   index derivation
 							 */
 
-#define CXLFLASH_MAX_CMDS               16
+#define CXLFLASH_MAX_CMDS               256
 #define CXLFLASH_MAX_CMDS_PER_LUN       CXLFLASH_MAX_CMDS
 
+/* RRQ for master issued cmds */
+#define NUM_RRQ_ENTRY                   CXLFLASH_MAX_CMDS
+
 
 static inline void check_sizes(void)
 {
@@ -149,7 +151,7 @@ struct afu_cmd {
 struct afu {
 	/* Stuff requiring alignment go first. */
 
-	u64 rrq_entry[NUM_RRQ_ENTRY];	/* 128B RRQ */
+	u64 rrq_entry[NUM_RRQ_ENTRY];	/* 2K RRQ */
 	/*
 	 * Command & data for AFU commands.
 	 */
--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -2305,7 +2305,7 @@ static struct scsi_host_template driver_
 	.eh_device_reset_handler = cxlflash_eh_device_reset_handler,
 	.eh_host_reset_handler = cxlflash_eh_host_reset_handler,
 	.change_queue_depth = cxlflash_change_queue_depth,
-	.cmd_per_lun = 16,
+	.cmd_per_lun = CXLFLASH_MAX_CMDS_PER_LUN,
 	.can_queue = CXLFLASH_MAX_CMDS,
 	.this_id = -1,
 	.sg_tablesize = SG_NONE,	/* No scatter gather support */