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Date: Tue, 29 Nov 2016 17:10:20 +0530
From: sunil.kovvuri@...il.com
To: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Sunil Goutham <sgoutham@...ium.com>
Subject: [PATCH net-next] net: thunderx: Fix transmit queue timeout issue
From: Sunil Goutham <sgoutham@...ium.com>
Transmit queue timeout issue is seen in two cases
- Due to a race condition btw setting stop_queue at xmit()
and checking for stopped_queue in NAPI poll routine, at times
transmission from a SQ comes to a halt. This is fixed
by using barriers and also added a check for SQ free descriptors,
incase SQ is stopped and there are only CQE_RX i.e no CQE_TX.
- Contrary to an assumption, a HW errata where HW doesn't stop transmission
even though there are not enough CQEs available for a CQE_TX is
not fixed in T88 pass 2.x. This results in a Qset error with
'CQ_WR_FULL' stalling transmission. This is fixed by adjusting
RXQ's RED levels for CQ level such that there is always enough
space left for CQE_TXs.
Signed-off-by: Sunil Goutham <sgoutham@...ium.com>
---
drivers/net/ethernet/cavium/thunder/nicvf_main.c | 52 ++++++++++++++++++----
drivers/net/ethernet/cavium/thunder/nicvf_queues.c | 24 ++--------
drivers/net/ethernet/cavium/thunder/nicvf_queues.h | 15 ++++---
3 files changed, 54 insertions(+), 37 deletions(-)
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
index 1eacec8..ced1802 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
@@ -644,6 +644,7 @@ static int nicvf_cq_intr_handler(struct net_device *netdev, u8 cq_idx,
struct cmp_queue *cq = &qs->cq[cq_idx];
struct cqe_rx_t *cq_desc;
struct netdev_queue *txq;
+ struct snd_queue *sq;
unsigned int tx_pkts = 0, tx_bytes = 0;
spin_lock_bh(&cq->lock);
@@ -709,16 +710,20 @@ static int nicvf_cq_intr_handler(struct net_device *netdev, u8 cq_idx,
done:
/* Wakeup TXQ if its stopped earlier due to SQ full */
- if (tx_done) {
+ sq = &nic->qs->sq[cq_idx];
+ if (tx_done ||
+ (atomic_read(&sq->free_cnt) >= MIN_SQ_DESC_PER_PKT_XMIT)) {
netdev = nic->pnicvf->netdev;
txq = netdev_get_tx_queue(netdev,
nicvf_netdev_qidx(nic, cq_idx));
if (tx_pkts)
netdev_tx_completed_queue(txq, tx_pkts, tx_bytes);
- nic = nic->pnicvf;
+ /* To read updated queue and carrier status */
+ smp_mb();
if (netif_tx_queue_stopped(txq) && netif_carrier_ok(netdev)) {
- netif_tx_start_queue(txq);
+ netif_tx_wake_queue(txq);
+ nic = nic->pnicvf;
this_cpu_inc(nic->drv_stats->txq_wake);
if (netif_msg_tx_err(nic))
netdev_warn(netdev,
@@ -1054,6 +1059,9 @@ static netdev_tx_t nicvf_xmit(struct sk_buff *skb, struct net_device *netdev)
struct nicvf *nic = netdev_priv(netdev);
int qid = skb_get_queue_mapping(skb);
struct netdev_queue *txq = netdev_get_tx_queue(netdev, qid);
+ struct nicvf *snic;
+ struct snd_queue *sq;
+ int tmp;
/* Check for minimum packet length */
if (skb->len <= ETH_HLEN) {
@@ -1061,13 +1069,39 @@ static netdev_tx_t nicvf_xmit(struct sk_buff *skb, struct net_device *netdev)
return NETDEV_TX_OK;
}
- if (!netif_tx_queue_stopped(txq) && !nicvf_sq_append_skb(nic, skb)) {
+ snic = nic;
+ /* Get secondary Qset's SQ structure */
+ if (qid >= MAX_SND_QUEUES_PER_QS) {
+ tmp = qid / MAX_SND_QUEUES_PER_QS;
+ snic = (struct nicvf *)nic->snicvf[tmp - 1];
+ if (!snic) {
+ netdev_warn(nic->netdev,
+ "Secondary Qset#%d's ptr not initialized\n",
+ tmp - 1);
+ dev_kfree_skb(skb);
+ return NETDEV_TX_OK;
+ }
+ qid = qid % MAX_SND_QUEUES_PER_QS;
+ }
+
+ sq = &snic->qs->sq[qid];
+ if (!netif_tx_queue_stopped(txq) &&
+ !nicvf_sq_append_skb(snic, sq, skb, qid)) {
netif_tx_stop_queue(txq);
- this_cpu_inc(nic->drv_stats->txq_stop);
- if (netif_msg_tx_err(nic))
- netdev_warn(netdev,
- "%s: Transmit ring full, stopping SQ%d\n",
- netdev->name, qid);
+
+ /* Barrier, so that stop_queue visible to other cpus */
+ smp_mb();
+
+ /* Check again, incase another cpu freed descriptors */
+ if (atomic_read(&sq->free_cnt) > MIN_SQ_DESC_PER_PKT_XMIT) {
+ netif_tx_start_queue(txq);
+ } else {
+ this_cpu_inc(nic->drv_stats->txq_stop);
+ if (netif_msg_tx_err(nic))
+ netdev_warn(netdev,
+ "%s: Transmit ring full, stopping SQ%d\n",
+ netdev->name, qid);
+ }
return NETDEV_TX_BUSY;
}
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
index 7b336cd..d2ac133 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
@@ -1190,30 +1190,12 @@ static int nicvf_sq_append_tso(struct nicvf *nic, struct snd_queue *sq,
}
/* Append an skb to a SQ for packet transfer. */
-int nicvf_sq_append_skb(struct nicvf *nic, struct sk_buff *skb)
+int nicvf_sq_append_skb(struct nicvf *nic, struct snd_queue *sq,
+ struct sk_buff *skb, u8 sq_num)
{
int i, size;
int subdesc_cnt, tso_sqe = 0;
- int sq_num, qentry;
- struct queue_set *qs;
- struct snd_queue *sq;
-
- sq_num = skb_get_queue_mapping(skb);
- if (sq_num >= MAX_SND_QUEUES_PER_QS) {
- /* Get secondary Qset's SQ structure */
- i = sq_num / MAX_SND_QUEUES_PER_QS;
- if (!nic->snicvf[i - 1]) {
- netdev_warn(nic->netdev,
- "Secondary Qset#%d's ptr not initialized\n",
- i - 1);
- return 1;
- }
- nic = (struct nicvf *)nic->snicvf[i - 1];
- sq_num = sq_num % MAX_SND_QUEUES_PER_QS;
- }
-
- qs = nic->qs;
- sq = &qs->sq[sq_num];
+ int qentry;
subdesc_cnt = nicvf_sq_subdesc_required(nic, skb);
if (subdesc_cnt > atomic_read(&sq->free_cnt))
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
index 20511f2..9e21046 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
@@ -88,13 +88,13 @@
/* RED and Backpressure levels of CQ for pkt reception
* For CQ, level is a measure of emptiness i.e 0x0 means full
- * eg: For CQ of size 4K, and for pass/drop levels of 128/96
- * HW accepts pkt if unused CQE >= 2048
- * RED accepts pkt if unused CQE < 2048 & >= 1536
- * DROPs pkts if unused CQE < 1536
+ * eg: For CQ of size 4K, and for pass/drop levels of 160/144
+ * HW accepts pkt if unused CQE >= 2560
+ * RED accepts pkt if unused CQE < 2304 & >= 2560
+ * DROPs pkts if unused CQE < 2304
*/
-#define RQ_PASS_CQ_LVL 128ULL
-#define RQ_DROP_CQ_LVL 96ULL
+#define RQ_PASS_CQ_LVL 160ULL
+#define RQ_DROP_CQ_LVL 144ULL
/* RED and Backpressure levels of RBDR for pkt reception
* For RBDR, level is a measure of fullness i.e 0x0 means empty
@@ -306,7 +306,8 @@ void nicvf_sq_disable(struct nicvf *nic, int qidx);
void nicvf_put_sq_desc(struct snd_queue *sq, int desc_cnt);
void nicvf_sq_free_used_descs(struct net_device *netdev,
struct snd_queue *sq, int qidx);
-int nicvf_sq_append_skb(struct nicvf *nic, struct sk_buff *skb);
+int nicvf_sq_append_skb(struct nicvf *nic, struct snd_queue *sq,
+ struct sk_buff *skb, u8 sq_num);
struct sk_buff *nicvf_get_rcv_skb(struct nicvf *nic, struct cqe_rx_t *cqe_rx);
void nicvf_rbdr_task(unsigned long data);
--
2.7.4
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