Commit a709423f authored by Julian Wiedmann's avatar Julian Wiedmann Committed by Heiko Carstens
Browse files

s390/qdio: remove internal polling in non-thinint path 



For non-thinint devices in LPAR, qdio polls an idle Input Queue for a
little while to catch more work. But platform support for thinints has
been around practically _forever_ by now, so this micro-optimization is
seeing 0 actual use. Remove it to reduce the overall complexity of the
hot path.

In the meantime we also grew support for driver-level polling
(eg. NAPI in qeth), so it's quite questionable how useful this would
actually be on current kernels.

Signed-off-by: default avatarJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 2bbf282a

drivers/s390/cio/qdio.h

+0 −3
Original line number Diff line number Diff line
@@ -15,7 +15,6 @@ 
#define QDIO_BUSY_BIT_PATIENCE		(100 << 12)	/* 100 microseconds */

#define QDIO_BUSY_BIT_RETRY_DELAY	10		/* 10 milliseconds */

#define QDIO_BUSY_BIT_RETRIES		1000		/* = 10s retry time */

#define QDIO_INPUT_THRESHOLD		(500 << 12)	/* 500 microseconds */



enum qdio_irq_states {

	QDIO_IRQ_STATE_INACTIVE,
@@ -181,8 +180,6 @@ struct qdio_input_q { 
	/* Batch of SBALs that we processed while polling the queue: */

	unsigned int batch_start;

	unsigned int batch_count;

	/* last time of noticing incoming data */

	u64 timestamp;

};



struct qdio_output_q {

drivers/s390/cio/qdio_main.c

+2 −24
Original line number Diff line number Diff line
@@ -510,14 +510,7 @@ static int get_inbound_buffer_frontier(struct qdio_q *q, unsigned int start) 


static int qdio_inbound_q_moved(struct qdio_q *q, unsigned int start)

{

	int count;



	count = get_inbound_buffer_frontier(q, start);



	if (count && !is_thinint_irq(q->irq_ptr) && MACHINE_IS_LPAR)

		q->u.in.timestamp = get_tod_clock();



	return count;

	return get_inbound_buffer_frontier(q, start);

}



static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
@@ -535,22 +528,7 @@ static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start) 
		/* more work coming */

		return 0;



	if (is_thinint_irq(q->irq_ptr))

		return 1;



	/* don't poll under z/VM */

	if (MACHINE_IS_VM)

	return 1;



	/*

	 * At this point we know, that inbound first_to_check

	 * has (probably) not moved (see qdio_inbound_processing).

	 */

	if (get_tod_clock_fast() > q->u.in.timestamp + QDIO_INPUT_THRESHOLD) {

		DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in done:%02x", start);

		return 1;

	} else

		return 0;

}



static inline void qdio_handle_aobs(struct qdio_q *q, int start, int count)