[SCSI] zfcp: add measurement data for average qdio queue utilisation

Provide measurement data for the utilisation of the QDIO outbound queue.
The additional value allows to calculate an average queue utilisation
by looking at the deltas per time unit. Needed for capacity planning.
It is up to user space to handle wrap-arounds of the 64 bit value.

The new counter neatly complements the existing counter for queue full
conditions. That is why, both statistics counter have been integrated.

Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/s390/scsi/zfcp_aux.c

@@ -501,6 +501,7 @@ int zfcp_adapter_enqueue(struct ccw_device *ccw_device)
 	spin_lock_init(&adapter->scsi_dbf_lock);
 	spin_lock_init(&adapter->rec_dbf_lock);
 	spin_lock_init(&adapter->req_q_lock);
+	spin_lock_init(&adapter->qdio_stat_lock);
 
 	rwlock_init(&adapter->erp_lock);
 	rwlock_init(&adapter->abort_lock);

drivers/s390/scsi/zfcp_def.h

@@ -445,6 +445,9 @@ struct zfcp_adapter {
 	spinlock_t		req_q_lock;	   /* for operations on queue */
 	int			req_q_pci_batch;   /* SBALs since PCI indication
 						      was last set */
+	ktime_t			req_q_time; /* time of last fill level change */
+	u64			req_q_util; /* for accounting */
+	spinlock_t		qdio_stat_lock;
 	u32			fsf_req_seq_no;	   /* FSF cmnd seq number */
 	wait_queue_head_t	request_wq;	   /* can be used to wait for
 						      more avaliable SBALs */

drivers/s390/scsi/zfcp_qdio.c

@@ -77,6 +77,23 @@ static void zfcp_qdio_zero_sbals(struct qdio_buffer *sbal[], int first, int cnt)
 	}
 }
 
+/* this needs to be called prior to updating the queue fill level */
+static void zfcp_qdio_account(struct zfcp_adapter *adapter)
+{
+	ktime_t now;
+	s64 span;
+	int free, used;
+
+	spin_lock(&adapter->qdio_stat_lock);
+	now = ktime_get();
+	span = ktime_us_delta(now, adapter->req_q_time);
+	free = max(0, atomic_read(&adapter->req_q.count));
+	used = QDIO_MAX_BUFFERS_PER_Q - free;
+	adapter->req_q_util += used * span;
+	adapter->req_q_time = now;
+	spin_unlock(&adapter->qdio_stat_lock);
+}
+
 static void zfcp_qdio_int_req(struct ccw_device *cdev, unsigned int qdio_err,
 			      int queue_no, int first, int count,
 			      unsigned long parm)
@@ -93,6 +110,7 @@ static void zfcp_qdio_int_req(struct ccw_device *cdev, unsigned int qdio_err,
 	/* cleanup all SBALs being program-owned now */
 	zfcp_qdio_zero_sbals(queue->sbal, first, count);
 
+	zfcp_qdio_account(adapter);
 	atomic_add(count, &queue->count);
 	wake_up(&adapter->request_wq);
 }
@@ -359,6 +377,8 @@ int zfcp_qdio_send(struct zfcp_fsf_req *fsf_req)
 		sbale->flags |= SBAL_FLAGS0_PCI;
 	}
 
+	zfcp_qdio_account(adapter);
+
 	retval = do_QDIO(adapter->ccw_device, QDIO_FLAG_SYNC_OUTPUT, 0, first,
 			 count);
 	if (unlikely(retval)) {

drivers/s390/scsi/zfcp_sysfs.c

@@ -487,7 +487,8 @@ static ssize_t zfcp_sysfs_adapter_q_full_show(struct device *dev,
 	struct zfcp_adapter *adapter =
 		(struct zfcp_adapter *) scsi_host->hostdata[0];
 
-	return sprintf(buf, "%d\n", atomic_read(&adapter->qdio_outb_full));
+	return sprintf(buf, "%d %llu\n", atomic_read(&adapter->qdio_outb_full),
+		       (unsigned long long)adapter->req_q_util);
 }
 static DEVICE_ATTR(queue_full, S_IRUGO, zfcp_sysfs_adapter_q_full_show, NULL);