[PATCH v1 05/10] mpi3mr: Fix performance regression caused by extended IRQ poll sleep

[Ranjan Kumar <ranjan.kumar@broadcom.com>]

Commit 24d7071d9645 ("scsi: mpi3mr: A performance fix") increased the
threaded IRQ poll sleep range from 2-20 us to 20-21 us to work around a
timer slack issue.

On kernels unaffected by the timer slack issue, the longer sleep interval
reduces reply queue processing efficiency and causes an approximately 7%
throughput regression on NVMe direct-attached RAID10 configurations.

Restore the IRQ poll sleep range to 2-20 us to recover the lost
throughput.

Fixes: 24d7071d9645 ("scsi: mpi3mr: A performance fix")
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Ranjan Kumar <ranjan.kumar@broadcom.com>
---
 drivers/scsi/mpi3mr/mpi3mr.h    | 2 +-
 drivers/scsi/mpi3mr/mpi3mr_fw.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mpi3mr/mpi3mr.h b/drivers/scsi/mpi3mr/mpi3mr.h
index 1f2f0951b560..1d11d7c69536 100644
--- a/drivers/scsi/mpi3mr/mpi3mr.h
+++ b/drivers/scsi/mpi3mr/mpi3mr.h
@@ -178,7 +178,7 @@ extern atomic64_t event_counter;
 #define MPI3MR_DEFAULT_SDEV_QD	32
 
 /* Definitions for Threaded IRQ poll*/
-#define MPI3MR_IRQ_POLL_SLEEP			20
+#define MPI3MR_IRQ_POLL_SLEEP			2
 #define MPI3MR_IRQ_POLL_TRIGGER_IOCOUNT		8
 
 /* Definitions for the controller security status*/
diff --git a/drivers/scsi/mpi3mr/mpi3mr_fw.c b/drivers/scsi/mpi3mr/mpi3mr_fw.c
index 496d7ca3ab37..32aeae20481e 100644
--- a/drivers/scsi/mpi3mr/mpi3mr_fw.c
+++ b/drivers/scsi/mpi3mr/mpi3mr_fw.c
@@ -744,7 +744,7 @@ static irqreturn_t mpi3mr_isr_poll(int irq, void *privdata)
 			    mpi3mr_process_op_reply_q(mrioc,
 				intr_info->op_reply_q);
 
-		usleep_range(MPI3MR_IRQ_POLL_SLEEP, MPI3MR_IRQ_POLL_SLEEP + 1);
+		usleep_range(MPI3MR_IRQ_POLL_SLEEP, 10 * MPI3MR_IRQ_POLL_SLEEP);
 
 	} while (atomic_read(&intr_info->op_reply_q->pend_ios) &&
 	    (num_op_reply < mrioc->max_host_ios));
-- 
2.47.3