[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>

4 files changed, 26 insertions, 1 deletions

diff --git a/drivers/s390/scsi/zfcp_aux.c b/drivers/s390/scsi/zfcp_aux.c
index 497986f6d64..969a3f09303 100644
--- a/drivers/s390/scsi/zfcp_aux.c
+++ b/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);
diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index 56302a1a4b6..a0cd4b08017 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/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 */
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c
index 33e0a206a0a..3d068709027 100644
--- a/drivers/s390/scsi/zfcp_qdio.c
+++ b/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)) {
diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c
index 899af2b45b1..9e9931af1b5 100644
--- a/drivers/s390/scsi/zfcp_sysfs.c
+++ b/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);