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Commit 1c721940 authored by Stefan Roscher's avatar Stefan Roscher Committed by Roland Dreier
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IB/ehca: Replace modulus operations in flush error completion path 



With the latest flush error completion patch we introduced modulus
operation to calculate the next index within a qmap.  Based on
comments from other mailing lists we decided to optimize this
operation by using an addition and an if-statement instead of modulus,
even though this is on the error path.

Signed-off-by: default avatarStefan Roscher <stefan.roscher@de.ibm.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
parent 75c21ae9

drivers/infiniband/hw/ehca/ehca_classes.h

+7 −0
Original line number Diff line number Diff line
@@ -175,6 +175,13 @@ struct ehca_queue_map { 
	unsigned int next_wqe_idx;   /* Idx to first wqe to be flushed */

};



/* function to calculate the next index for the qmap */

static inline unsigned int next_index(unsigned int cur_index, unsigned int limit)

{

	unsigned int temp = cur_index + 1;

	return (temp == limit) ? 0 : temp;

}



struct ehca_qp {

	union {

		struct ib_qp ib_qp;

drivers/infiniband/hw/ehca/ehca_qp.c

+6 −6
Original line number Diff line number Diff line
@@ -1138,14 +1138,14 @@ static int calc_left_cqes(u64 wqe_p, struct ipz_queue *ipz_queue, 
		return -EFAULT;

	}



	tail_idx = (qmap->tail + 1) % qmap->entries;

	tail_idx = next_index(qmap->tail, qmap->entries);

	wqe_idx = q_ofs / ipz_queue->qe_size;



	/* check all processed wqes, whether a cqe is requested or not */

	while (tail_idx != wqe_idx) {

		if (qmap->map[tail_idx].cqe_req)

			qmap->left_to_poll++;

		tail_idx = (tail_idx + 1) % qmap->entries;

		tail_idx = next_index(tail_idx, qmap->entries);

	}

	/* save index in queue, where we have to start flushing */

	qmap->next_wqe_idx = wqe_idx;
@@ -1195,14 +1195,14 @@ static int check_for_left_cqes(struct ehca_qp *my_qp, struct ehca_shca *shca) 
	} else {

		spin_lock_irqsave(&my_qp->send_cq->spinlock, flags);

		my_qp->sq_map.left_to_poll = 0;

		my_qp->sq_map.next_wqe_idx = (my_qp->sq_map.tail + 1) %

						my_qp->sq_map.entries;

		my_qp->sq_map.next_wqe_idx = next_index(my_qp->sq_map.tail,

							my_qp->sq_map.entries);

		spin_unlock_irqrestore(&my_qp->send_cq->spinlock, flags);



		spin_lock_irqsave(&my_qp->recv_cq->spinlock, flags);

		my_qp->rq_map.left_to_poll = 0;

		my_qp->rq_map.next_wqe_idx = (my_qp->rq_map.tail + 1) %

						my_qp->rq_map.entries;

		my_qp->rq_map.next_wqe_idx = next_index(my_qp->rq_map.tail,

							my_qp->rq_map.entries);

		spin_unlock_irqrestore(&my_qp->recv_cq->spinlock, flags);

	}

drivers/infiniband/hw/ehca/ehca_reqs.c

+6 −7
Original line number Diff line number Diff line
@@ -726,13 +726,13 @@ static inline int ehca_poll_cq_one(struct ib_cq *cq, struct ib_wc *wc) 
		 * set left_to_poll to 0 because in error state, we will not

		 * get any additional CQEs

		 */

		my_qp->sq_map.next_wqe_idx = (my_qp->sq_map.tail + 1) %

						my_qp->sq_map.entries;

		my_qp->sq_map.next_wqe_idx = next_index(my_qp->sq_map.tail,

							my_qp->sq_map.entries);

		my_qp->sq_map.left_to_poll = 0;

		ehca_add_to_err_list(my_qp, 1);



		my_qp->rq_map.next_wqe_idx = (my_qp->rq_map.tail + 1) %

						my_qp->rq_map.entries;

		my_qp->rq_map.next_wqe_idx = next_index(my_qp->rq_map.tail,

							my_qp->rq_map.entries);

		my_qp->rq_map.left_to_poll = 0;

		if (HAS_RQ(my_qp))

			ehca_add_to_err_list(my_qp, 0);
@@ -860,9 +860,8 @@ static int generate_flush_cqes(struct ehca_qp *my_qp, struct ib_cq *cq, 


		/* mark as reported and advance next_wqe pointer */

		qmap_entry->reported = 1;

		qmap->next_wqe_idx++;

		if (qmap->next_wqe_idx == qmap->entries)

			qmap->next_wqe_idx = 0;

		qmap->next_wqe_idx = next_index(qmap->next_wqe_idx,

						qmap->entries);

		qmap_entry = &qmap->map[qmap->next_wqe_idx];



		wc++; nr++;