[PATCH 4.4 06/30] cxlflash: Increase cmd_per_lun for better throughput

Greg Kroah-Hartman
2017-03-24T18:04:46Z

From: Manoj N. Kumar <manoj@linux.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@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Reviewed-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 */