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Commit 6022943e authored by Bryan O'Sullivan's avatar Bryan O'Sullivan Committed by Roland Dreier
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IB/ipath: Limit # of packets sent without an ACK received 



The sender requests an ACK every 1/2 MB to avoid retransmit timeouts that
were causing MVAPICH mod_bw to fail after a predictable number of sends.

Signed-off-by: default avatarBryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
parent fd6a79a7

drivers/infiniband/hw/ipath/ipath_qp.c

+2 −1
Original line number Diff line number Diff line
@@ -342,6 +342,7 @@ static void ipath_reset_qp(struct ipath_qp *qp) 
	qp->s_last = 0;

	qp->s_ssn = 1;

	qp->s_lsn = 0;

	qp->s_wait_credit = 0;

	if (qp->r_rq.wq) {

		qp->r_rq.wq->head = 0;

		qp->r_rq.wq->tail = 0;
@@ -516,7 +517,7 @@ int ipath_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr, 
		qp->remote_qpn = attr->dest_qp_num;



	if (attr_mask & IB_QP_SQ_PSN) {

		qp->s_next_psn = attr->sq_psn;

		qp->s_psn = qp->s_next_psn = attr->sq_psn;

		qp->s_last_psn = qp->s_next_psn - 1;

	}

drivers/infiniband/hw/ipath/ipath_rc.c

+29 −18
Original line number Diff line number Diff line
@@ -201,6 +201,18 @@ int ipath_make_rc_req(struct ipath_qp *qp, 
	    qp->s_rnr_timeout)

		goto done;



	/* Limit the number of packets sent without an ACK. */

	if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT) > 0) {

		qp->s_wait_credit = 1;

		dev->n_rc_stalls++;

		spin_lock(&dev->pending_lock);

		if (list_empty(&qp->timerwait))

			list_add_tail(&qp->timerwait,

				      &dev->pending[dev->pending_index]);

		spin_unlock(&dev->pending_lock);

		goto done;

	}



	/* header size in 32-bit words LRH+BTH = (8+12)/4. */

	hwords = 5;

	bth0 = 0;
@@ -221,7 +233,7 @@ int ipath_make_rc_req(struct ipath_qp *qp, 
			/* Check if send work queue is empty. */

			if (qp->s_tail == qp->s_head)

				goto done;

			qp->s_psn = wqe->psn = qp->s_next_psn;

			wqe->psn = qp->s_next_psn;

			newreq = 1;

		}

		/*
@@ -393,12 +405,6 @@ int ipath_make_rc_req(struct ipath_qp *qp, 
		ss = &qp->s_sge;

		len = qp->s_len;

		if (len > pmtu) {

			/*

			 * Request an ACK every 1/2 MB to avoid retransmit

			 * timeouts.

			 */

			if (((wqe->length - len) % (512 * 1024)) == 0)

				bth2 |= 1 << 31;

			len = pmtu;

			break;

		}
@@ -435,12 +441,6 @@ int ipath_make_rc_req(struct ipath_qp *qp, 
		ss = &qp->s_sge;

		len = qp->s_len;

		if (len > pmtu) {

			/*

			 * Request an ACK every 1/2 MB to avoid retransmit

			 * timeouts.

			 */

			if (((wqe->length - len) % (512 * 1024)) == 0)

				bth2 |= 1 << 31;

			len = pmtu;

			break;

		}
@@ -498,6 +498,8 @@ int ipath_make_rc_req(struct ipath_qp *qp, 
		 */

		goto done;

	}

	if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT - 1) >= 0)

		bth2 |= 1 << 31;	/* Request ACK. */

	qp->s_len -= len;

	qp->s_hdrwords = hwords;

	qp->s_cur_sge = ss;
@@ -737,6 +739,15 @@ bail: 
	return;

}



static inline void update_last_psn(struct ipath_qp *qp, u32 psn)

{

	if (qp->s_wait_credit) {

		qp->s_wait_credit = 0;

		tasklet_hi_schedule(&qp->s_task);

	}

	qp->s_last_psn = psn;

}



/**

 * do_rc_ack - process an incoming RC ACK

 * @qp: the QP the ACK came in on
@@ -805,7 +816,7 @@ static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode) 
			 * The last valid PSN seen is the previous

			 * request's.

			 */

			qp->s_last_psn = wqe->psn - 1;

			update_last_psn(qp, wqe->psn - 1);

			/* Retry this request. */

			ipath_restart_rc(qp, wqe->psn, &wc);

			/*
@@ -864,7 +875,7 @@ static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode) 
		ipath_get_credit(qp, aeth);

		qp->s_rnr_retry = qp->s_rnr_retry_cnt;

		qp->s_retry = qp->s_retry_cnt;

		qp->s_last_psn = psn;

		update_last_psn(qp, psn);

		ret = 1;

		goto bail;
@@ -883,7 +894,7 @@ static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode) 
			goto bail;



		/* The last valid PSN is the previous PSN. */

		qp->s_last_psn = psn - 1;

		update_last_psn(qp, psn - 1);



		dev->n_rc_resends += (int)qp->s_psn - (int)psn;
@@ -898,7 +909,7 @@ static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode) 
	case 3:		/* NAK */

		/* The last valid PSN seen is the previous request's. */

		if (qp->s_last != qp->s_tail)

			qp->s_last_psn = wqe->psn - 1;

			update_last_psn(qp, wqe->psn - 1);

		switch ((aeth >> IPATH_AETH_CREDIT_SHIFT) &

			IPATH_AETH_CREDIT_MASK) {

		case 0:	/* PSN sequence error */
@@ -1071,7 +1082,7 @@ static inline void ipath_rc_rcv_resp(struct ipath_ibdev *dev, 
		 * since we don't want s_sge modified.

		 */

		qp->s_len -= pmtu;

		qp->s_last_psn = psn;

		update_last_psn(qp, psn);

		spin_unlock_irqrestore(&qp->s_lock, flags);

		ipath_copy_sge(&qp->s_sge, data, pmtu);

		goto bail;

drivers/infiniband/hw/ipath/ipath_verbs.c

+2 −1
Original line number Diff line number Diff line
@@ -1683,6 +1683,7 @@ static ssize_t show_stats(struct class_device *cdev, char *buf) 
		      "RC OTH NAKs %d\n"

		      "RC timeouts %d\n"

		      "RC RDMA dup %d\n"

		      "RC stalls   %d\n"

		      "piobuf wait %d\n"

		      "no piobuf   %d\n"

		      "PKT drops   %d\n"
@@ -1690,7 +1691,7 @@ static ssize_t show_stats(struct class_device *cdev, char *buf) 
		      dev->n_rc_resends, dev->n_rc_qacks, dev->n_rc_acks,

		      dev->n_seq_naks, dev->n_rdma_seq, dev->n_rnr_naks,

		      dev->n_other_naks, dev->n_timeouts,

		      dev->n_rdma_dup_busy, dev->n_piowait,

		      dev->n_rdma_dup_busy, dev->n_rc_stalls, dev->n_piowait,

		      dev->n_no_piobuf, dev->n_pkt_drops, dev->n_wqe_errs);

	for (i = 0; i < ARRAY_SIZE(dev->opstats); i++) {

		const struct ipath_opcode_stats *si = &dev->opstats[i];

drivers/infiniband/hw/ipath/ipath_verbs.h

+4 −0
Original line number Diff line number Diff line
@@ -370,6 +370,7 @@ struct ipath_qp { 
	u8 s_rnr_retry_cnt;

	u8 s_retry;		/* requester retry counter */

	u8 s_rnr_retry;		/* requester RNR retry counter */

	u8 s_wait_credit;	/* limit number of unacked packets sent */

	u8 s_pkey_index;	/* PKEY index to use */

	u8 timeout;		/* Timeout for this QP */

	enum ib_mtu path_mtu;
@@ -393,6 +394,8 @@ struct ipath_qp { 
#define IPATH_S_BUSY		0

#define IPATH_S_SIGNAL_REQ_WR	1



#define IPATH_PSN_CREDIT	2048



/*

 * Since struct ipath_swqe is not a fixed size, we can't simply index into

 * struct ipath_qp.s_wq.  This function does the array index computation.
@@ -521,6 +524,7 @@ struct ipath_ibdev { 
	u32 n_rnr_naks;

	u32 n_other_naks;

	u32 n_timeouts;

	u32 n_rc_stalls;

	u32 n_pkt_drops;

	u32 n_vl15_dropped;

	u32 n_wqe_errs;