[S390] qdio: speed up multicast traffic on full HiperSocket queue

If an asynchronous HiperSockets queue runs full, no further packet
can be sent. In this case the next initiative to give transmitted
skbs back to the stack is triggered only by a 10-seconds qdio timer.
This timer has been introduced for low multicast traffic scenarios
to guarantee freeing of skbs in a limited amount of time. For high
HiperSocket multicast traffic scenarios progress checking on the
outbound queue should be enforced by tasklet rescheduling.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/qdio.h

@@ -16,6 +16,14 @@
 #define QDIO_BUSY_BIT_GIVE_UP		2000000	/* 2 seconds = eternity */
 #define QDIO_INPUT_THRESHOLD		500	/* 500 microseconds */
 
+/*
+ * if an asynchronous HiperSockets queue runs full, the 10 seconds timer wait
+ * till next initiative to give transmitted skbs back to the stack is too long.
+ * Therefore polling is started in case of multicast queue is filled more
+ * than 50 percent.
+ */
+#define QDIO_IQDIO_POLL_LVL		65	/* HS multicast queue */
+
 enum qdio_irq_states {
 	QDIO_IRQ_STATE_INACTIVE,
 	QDIO_IRQ_STATE_ESTABLISHED,

drivers/s390/cio/qdio_main.c

@@ -851,6 +851,12 @@ static void __qdio_outbound_processing(struct qdio_q *q)
 	if (queue_type(q) == QDIO_IQDIO_QFMT && !multicast_outbound(q))
 		return;
 
+	if ((queue_type(q) == QDIO_IQDIO_QFMT) &&
+	    (atomic_read(&q->nr_buf_used)) > QDIO_IQDIO_POLL_LVL) {
+		tasklet_schedule(&q->tasklet);
+		return;
+	}
+
 	if (q->u.out.pci_out_enabled)
 		return;