[S390] qdio: outbound tasklet scan threshold

Introduce a scan treshold for the qdio outbound queues. By setting the
threshold the driver can tell qdio after how much used SBALs qdio
should schedule the outbound tasklet that scans the queue for finished
SBALs. The threshold is specific by the drivers because a
Hipersockets device is much faster in utilizing outbound buffers than a
ZFCP or OSA device.

The default values after how many used SBALs the tasklet should run are:

OSA:          > 31 SBALs
Hipersockets: > 7 SBALs
zfcp:         > 55 SBALs

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 10 insertions, 1 deletions

diff --git a/drivers/s390/cio/qdio.h b/drivers/s390/cio/qdio.h
index 9b6ea3ca3ece..a77aa9109cfd 100644
--- a/drivers/s390/cio/qdio.h
+++ b/drivers/s390/cio/qdio.h
@@ -249,6 +249,8 @@ struct qdio_output_q {
         int use_enh_siga;
         /* timer to check for more outbound work */
         struct timer_list timer;
+        /* used SBALs before tasklet schedule */
+        int scan_threshold;
 };
 
 /*
diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index 6621de94f3ad..4c0109900c74 100644
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -1492,7 +1492,13 @@ static int handle_outbound(struct qdio_q *q, unsigned int callflags,
                 qperf_inc(q, fast_requeue);
 
 out:
-        tasklet_schedule(&q->tasklet);
+        /* in case of SIGA errors we must process the error immediately */
+        if (used >= q->u.out.scan_threshold || rc)
+                tasklet_schedule(&q->tasklet);
+        else
+                /* free the SBALs in case of no further traffic */
+                if (!timer_pending(&q->u.out.timer))
+                        mod_timer(&q->u.out.timer, jiffies + HZ);
         return rc;
 }
 
diff --git a/drivers/s390/cio/qdio_setup.c b/drivers/s390/cio/qdio_setup.c
index a13cf7ec64b2..635f35dc8466 100644
--- a/drivers/s390/cio/qdio_setup.c
+++ b/drivers/s390/cio/qdio_setup.c
@@ -178,6 +178,7 @@ static void setup_queues(struct qdio_irq *irq_ptr,
                 setup_queues_misc(q, irq_ptr, qdio_init->output_handler, i);
 
                 q->is_input_q = 0;
+                q->u.out.scan_threshold = qdio_init->scan_threshold;
                 setup_storage_lists(q, irq_ptr, output_sbal_array, i);
                 output_sbal_array += QDIO_MAX_BUFFERS_PER_Q;