scsi: mpt3sas: Use high iops queues under some circumstances

The driver will use round-robin method for io submission in batches within
the high iops queues when the number of in-flight ios on the target device
is larger than 8. Otherwise the driver will use low latency reply queues.

Signed-off-by: Suganath Prabu S <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/mpt3sas/mpt3sas_base.c

···
 }
 
 /**
+ * _base_get_high_iops_msix_index - get the msix index of
+ *				high iops queues
+ * @ioc: per adapter object
+ * @scmd: scsi_cmnd object
+ *
+ * Returns: msix index of high iops reply queues.
+ * i.e. high iops reply queue on which IO request's
+ * reply should be posted by the HBA firmware.
+ */
+static inline u8
+_base_get_high_iops_msix_index(struct MPT3SAS_ADAPTER *ioc,
+	struct scsi_cmnd *scmd)
+{
+	/**
+	 * Round robin the IO interrupts among the high iops
+	 * reply queues in terms of batch count 16 when outstanding
+	 * IOs on the target device is >=8.
+	 */
+	if (atomic_read(&scmd->device->device_busy) >
+	    MPT3SAS_DEVICE_HIGH_IOPS_DEPTH)
+		return base_mod64((
+		    atomic64_add_return(1, &ioc->high_iops_outstanding) /
+		    MPT3SAS_HIGH_IOPS_BATCH_COUNT),
+		    MPT3SAS_HIGH_IOPS_REPLY_QUEUES);
+
+	return _base_get_msix_index(ioc, scmd);
+}
+
+/**
  * mpt3sas_base_get_smid - obtain a free smid from internal queue
  * @ioc: per adapter object
  * @cb_idx: callback index
···
 		ioc->build_sg_scmd = &_base_build_sg_scmd;
 		ioc->build_sg = &_base_build_sg;
 		ioc->build_zero_len_sge = &_base_build_zero_len_sge;
+		ioc->get_msix_index_for_smlio = &_base_get_msix_index;
 		break;
 	case MPI25_VERSION:
 	case MPI26_VERSION:
···
 		ioc->build_nvme_prp = &_base_build_nvme_prp;
 		ioc->build_zero_len_sge = &_base_build_zero_len_sge_ieee;
 		ioc->sge_size_ieee = sizeof(Mpi2IeeeSgeSimple64_t);
-
+		if (ioc->high_iops_queues)
+			ioc->get_msix_index_for_smlio =
+					&_base_get_high_iops_msix_index;
+		else
+			ioc->get_msix_index_for_smlio = &_base_get_msix_index;
 		break;
 	}
 	if (ioc->atomic_desc_capable) {

drivers/scsi/mpt3sas/mpt3sas_base.h

···
 #define VIRTUAL_IO_FAILED_RETRY			(0x32010081)
 
 /* High IOPs definitions */
+#define MPT3SAS_DEVICE_HIGH_IOPS_DEPTH		8
 #define MPT3SAS_HIGH_IOPS_REPLY_QUEUES		8
+#define MPT3SAS_HIGH_IOPS_BATCH_COUNT		16
 #define MPT3SAS_GEN35_MAX_MSIX_QUEUES		128
 
 /* OEM Specific Flags will come from OEM specific header files */
···
 	u16 funcdep);
 typedef void (*PUT_SMID_DEFAULT) (struct MPT3SAS_ADAPTER *ioc, u16 smid);
 typedef u32 (*BASE_READ_REG) (const volatile void __iomem *addr);
+/*
+ * To get high iops reply queue's msix index when high iops mode is enabled
+ * else get the msix index of general reply queues.
+ */
+typedef u8 (*GET_MSIX_INDEX) (struct MPT3SAS_ADAPTER *ioc,
+	struct scsi_cmnd *scmd);
 
 /* IOC Facts and Port Facts converted from little endian to cpu */
 union mpi3_version_union {
···
  * @cpu_msix_table: table for mapping cpus to msix index
  * @cpu_msix_table_sz: table size
  * @total_io_cnt: Gives total IO count, used to load balance the interrupts
+ * @high_iops_outstanding: used to load balance the interrupts
+ *				within high iops reply queues
  * @msix_load_balance: Enables load balancing of interrupts across
  * the multiple MSIXs
  * @schedule_dead_ioc_flush_running_cmds: callback to flush pending commands
···
  *	crash. To avoid the above race condition we use mutex syncrhonization
  *	which ensures the syncrhonization between cli/sysfs_show path.
  * @atomic_desc_capable: Atomic Request Descriptor support.
+ * @GET_MSIX_INDEX: Get the msix index of high iops queues.
  */
 struct MPT3SAS_ADAPTER {
 	struct list_head list;
···
 	MPT3SAS_FLUSH_RUNNING_CMDS schedule_dead_ioc_flush_running_cmds;
 	u32             non_operational_loop;
 	atomic64_t      total_io_cnt;
+	atomic64_t	high_iops_outstanding;
 	bool            msix_load_balance;
 	u16		thresh_hold;
 	u8		high_iops_queues;
···
 	PUT_SMID_IO_FP_HIP put_smid_fast_path;
 	PUT_SMID_IO_FP_HIP put_smid_hi_priority;
 	PUT_SMID_DEFAULT put_smid_default;
-
+	GET_MSIX_INDEX get_msix_index_for_smlio;
 };
 
 typedef u8 (*MPT_CALLBACK)(struct MPT3SAS_ADAPTER *ioc, u16 smid, u8 msix_index,