[PATCH 1 of 28] IB/ipath - limit # of packets sent without an ACK received

Bryan O'Sullivan
2006-09-28T16:01:48Z

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: Bryan O'Sullivan <bryan.osullivan@qlogic.com>

diff -r f1b431dca1f9 -r c46292ccb0f5 drivers/infiniband/hw/ipath/ipath_qp.c
--- a/drivers/infiniband/hw/ipath/ipath_qp.c Thu Sep 28 08:57:12 2006 -0700
+++ b/drivers/infiniband/hw/ipath/ipath_qp.c Thu Sep 28 08:57:12 2006 -0700
@@ -342,6 +342,7 @@ static void ipath_reset_qp(struct ipath_
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,
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;
}

diff -r f1b431dca1f9 -r c46292ccb0f5 drivers/infiniband/hw/ipath/ipath_rc.c
--- a/drivers/infiniband/hw/ipath/ipath_rc.c Thu Sep 28 08:57:12 2006 -0700
+++ b/drivers/infiniband/hw/ipath/ipath_rc.c Thu Sep 28 08:57:12 2006 -0700
@@ -201,6 +201,18 @@ int ipath_make_rc_req(struct ipath_qp *q
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 *q
/* 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 *q
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 *q
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 *q
*/
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
* 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
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
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
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(str
* 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;
diff -r f1b431dca1f9 -r c46292ccb0f5 drivers/infiniband/hw/ipath/ipath_verbs.c
--- a/drivers/infiniband/hw/ipath/ipath_verbs.c Thu Sep 28 08:57:12 2006 -0700
+++ b/drivers/infiniband/hw/ipath/ipath_verbs.c Thu Sep 28 08:57:12 2006 -0700
@@ -1683,6 +1683,7 @@ static ssize_t show_stats(struct class_d
"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_d
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];
diff -r f1b431dca1f9 -r c46292ccb0f5 drivers/infiniband/hw/ipath/ipath_verbs.h
--- a/drivers/infiniband/hw/ipath/ipath_verbs.h Thu Sep 28 08:57:12 2006 -0700
+++ b/drivers/infiniband/hw/ipath/ipath_verbs.h Thu Sep 28 08:57:12 2006 -0700
@@ -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;
@@ -392,6 +393,8 @@ 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
@@ -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;