mlx4: remove mlx4_en_low_latency_recv()

Busy polling can now be handled in generic NAPI poll infrastructure.
This removes complexity and fast path overhead :

mlx4 used two spin_lock()/spin_unlock() pair per napi->poll() call
in mlx4_en_cq_lock_napi()/mlx4_en_cq_unlock_napi()

Tested:

Without busy polling :

lpaa23:~# echo 0 >/proc/sys/net/core/busy_read
lpaa24:~# echo 0 >/proc/sys/net/core/busy_read
lpaa23:~# ./netperf -H lpaa24 -t TCP_RR
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lpaa24.prod.google.com () port 0 AF_INET : first burst 0
Local /Remote
Socket Size   Request  Resp.   Elapsed  Trans.
Send   Recv   Size     Size    Time     Rate
bytes  Bytes  bytes    bytes   secs.    per sec

16384  87380  1        1       10.00    47330.78

With busy polling :

lpaa23:~# echo 70 >/proc/sys/net/core/busy_read
lpaa24:~# echo 70 >/proc/sys/net/core/busy_read
lpaa23:~# ./netperf -H lpaa24 -t TCP_RR
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lpaa24.prod.google.com () port 0 AF_INET : first burst 0
Local /Remote
Socket Size   Request  Resp.   Elapsed  Trans.
Send   Recv   Size     Size    Time     Rate
bytes  Bytes  bytes    bytes   secs.    per sec

16384  87380  1        1       10.00    97643.55
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_ethtool.c

@@ -337,11 +337,7 @@ static int mlx4_en_get_sset_count(struct net_device *dev, int sset)
 	case ETH_SS_STATS:
 		return bitmap_iterator_count(&it) +
 			(priv->tx_ring_num * 2) +
-#ifdef CONFIG_NET_RX_BUSY_POLL
-			(priv->rx_ring_num * 5);
-#else
 			(priv->rx_ring_num * 2);
-#endif
 	case ETH_SS_TEST:
 		return MLX4_EN_NUM_SELF_TEST - !(priv->mdev->dev->caps.flags
 					& MLX4_DEV_CAP_FLAG_UC_LOOPBACK) * 2;
@@ -408,11 +404,6 @@ static void mlx4_en_get_ethtool_stats(struct net_device *dev,
 	for (i = 0; i < priv->rx_ring_num; i++) {
 		data[index++] = priv->rx_ring[i]->packets;
 		data[index++] = priv->rx_ring[i]->bytes;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-		data[index++] = priv->rx_ring[i]->yields;
-		data[index++] = priv->rx_ring[i]->misses;
-		data[index++] = priv->rx_ring[i]->cleaned;
-#endif
 	}
 	spin_unlock_bh(&priv->stats_lock);
 
@@ -486,14 +477,6 @@ static void mlx4_en_get_strings(struct net_device *dev,
 				"rx%d_packets", i);
 			sprintf(data + (index++) * ETH_GSTRING_LEN,
 				"rx%d_bytes", i);
-#ifdef CONFIG_NET_RX_BUSY_POLL
-			sprintf(data + (index++) * ETH_GSTRING_LEN,
-				"rx%d_napi_yield", i);
-			sprintf(data + (index++) * ETH_GSTRING_LEN,
-				"rx%d_misses", i);
-			sprintf(data + (index++) * ETH_GSTRING_LEN,
-				"rx%d_cleaned", i);
-#endif
 		}
 		break;
 	case ETH_SS_PRIV_FLAGS:

drivers/net/ethernet/mellanox/mlx4/en_netdev.c

@@ -69,34 +69,6 @@ int mlx4_en_setup_tc(struct net_device *dev, u8 up)
 	return 0;
 }
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-/* must be called with local_bh_disable()d */
-static int mlx4_en_low_latency_recv(struct napi_struct *napi)
-{
-	struct mlx4_en_cq *cq = container_of(napi, struct mlx4_en_cq, napi);
-	struct net_device *dev = cq->dev;
-	struct mlx4_en_priv *priv = netdev_priv(dev);
-	struct mlx4_en_rx_ring *rx_ring = priv->rx_ring[cq->ring];
-	int done;
-
-	if (!priv->port_up)
-		return LL_FLUSH_FAILED;
-
-	if (!mlx4_en_cq_lock_poll(cq))
-		return LL_FLUSH_BUSY;
-
-	done = mlx4_en_process_rx_cq(dev, cq, 4);
-	if (likely(done))
-		rx_ring->cleaned += done;
-	else
-		rx_ring->misses++;
-
-	mlx4_en_cq_unlock_poll(cq);
-
-	return done;
-}
-#endif	/* CONFIG_NET_RX_BUSY_POLL */
-
 #ifdef CONFIG_RFS_ACCEL
 
 struct mlx4_en_filter {
@@ -1561,8 +1533,6 @@ int mlx4_en_start_port(struct net_device *dev)
 	for (i = 0; i < priv->rx_ring_num; i++) {
 		cq = priv->rx_cq[i];
 
-		mlx4_en_cq_init_lock(cq);
-
 		err = mlx4_en_init_affinity_hint(priv, i);
 		if (err) {
 			en_err(priv, "Failed preparing IRQ affinity hint\n");
@@ -1859,13 +1829,6 @@ void mlx4_en_stop_port(struct net_device *dev, int detach)
 	for (i = 0; i < priv->rx_ring_num; i++) {
 		struct mlx4_en_cq *cq = priv->rx_cq[i];
 
-		local_bh_disable();
-		while (!mlx4_en_cq_lock_napi(cq)) {
-			pr_info("CQ %d locked\n", i);
-			mdelay(1);
-		}
-		local_bh_enable();
-
 		napi_synchronize(&cq->napi);
 		mlx4_en_deactivate_rx_ring(priv, priv->rx_ring[i]);
 		mlx4_en_deactivate_cq(priv, cq);
@@ -2503,9 +2466,6 @@ static const struct net_device_ops mlx4_netdev_ops = {
 	.ndo_setup_tc		= mlx4_en_setup_tc,
 #ifdef CONFIG_RFS_ACCEL
 	.ndo_rx_flow_steer	= mlx4_en_filter_rfs,
-#endif
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	.ndo_busy_poll		= mlx4_en_low_latency_recv,
 #endif
 	.ndo_get_phys_port_id	= mlx4_en_get_phys_port_id,
 #ifdef CONFIG_MLX4_EN_VXLAN

drivers/net/ethernet/mellanox/mlx4/en_rx.c

@@ -873,10 +873,8 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 		 * - TCP/IP (v4)
 		 * - without IP options
 		 * - not an IP fragment
-		 * - no LLS polling in progress
 		 */
-		if (!mlx4_en_cq_busy_polling(cq) &&
-		    (dev->features & NETIF_F_GRO)) {
+		if (dev->features & NETIF_F_GRO) {
 			struct sk_buff *gro_skb = napi_get_frags(&cq->napi);
 			if (!gro_skb)
 				goto next;
@@ -992,11 +990,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 
 		skb_mark_napi_id(skb, &cq->napi);
 
-		if (!mlx4_en_cq_busy_polling(cq))
-			napi_gro_receive(&cq->napi, skb);
-		else
-			netif_receive_skb(skb);
-
+		napi_gro_receive(&cq->napi, skb);
 next:
 		for (nr = 0; nr < priv->num_frags; nr++)
 			mlx4_en_free_frag(priv, frags, nr);
@@ -1038,13 +1032,8 @@ int mlx4_en_poll_rx_cq(struct napi_struct *napi, int budget)
 	struct mlx4_en_priv *priv = netdev_priv(dev);
 	int done;
 
-	if (!mlx4_en_cq_lock_napi(cq))
-		return budget;
-
 	done = mlx4_en_process_rx_cq(dev, cq, budget);
 
-	mlx4_en_cq_unlock_napi(cq);
-
 	/* If we used up all the quota - we're probably not done yet... */
 	if (done == budget) {
 		const struct cpumask *aff;

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

@@ -320,11 +320,6 @@ struct mlx4_en_rx_ring {
 	void *rx_info;
 	unsigned long bytes;
 	unsigned long packets;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	unsigned long yields;
-	unsigned long misses;
-	unsigned long cleaned;
-#endif
 	unsigned long csum_ok;
 	unsigned long csum_none;
 	unsigned long csum_complete;
@@ -347,18 +342,6 @@ struct mlx4_en_cq {
 	struct mlx4_cqe *buf;
 #define MLX4_EN_OPCODE_ERROR	0x1e
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	unsigned int state;
-#define MLX4_EN_CQ_STATE_IDLE        0
-#define MLX4_EN_CQ_STATE_NAPI     1    /* NAPI owns this CQ */
-#define MLX4_EN_CQ_STATE_POLL     2    /* poll owns this CQ */
-#define MLX4_CQ_LOCKED (MLX4_EN_CQ_STATE_NAPI | MLX4_EN_CQ_STATE_POLL)
-#define MLX4_EN_CQ_STATE_NAPI_YIELD  4    /* NAPI yielded this CQ */
-#define MLX4_EN_CQ_STATE_POLL_YIELD  8    /* poll yielded this CQ */
-#define CQ_YIELD (MLX4_EN_CQ_STATE_NAPI_YIELD | MLX4_EN_CQ_STATE_POLL_YIELD)
-#define CQ_USER_PEND (MLX4_EN_CQ_STATE_POLL | MLX4_EN_CQ_STATE_POLL_YIELD)
-	spinlock_t poll_lock; /* protects from LLS/napi conflicts */
-#endif  /* CONFIG_NET_RX_BUSY_POLL */
 	struct irq_desc *irq_desc;
 };
 
@@ -622,117 +605,6 @@ static inline struct mlx4_cqe *mlx4_en_get_cqe(void *buf, int idx, int cqe_sz)
 	return buf + idx * cqe_sz;
 }
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-static inline void mlx4_en_cq_init_lock(struct mlx4_en_cq *cq)
-{
-	spin_lock_init(&cq->poll_lock);
-	cq->state = MLX4_EN_CQ_STATE_IDLE;
-}
-
-/* called from the device poll rutine to get ownership of a cq */
-static inline bool mlx4_en_cq_lock_napi(struct mlx4_en_cq *cq)
-{
-	int rc = true;
-	spin_lock(&cq->poll_lock);
-	if (cq->state & MLX4_CQ_LOCKED) {
-		WARN_ON(cq->state & MLX4_EN_CQ_STATE_NAPI);
-		cq->state |= MLX4_EN_CQ_STATE_NAPI_YIELD;
-		rc = false;
-	} else
-		/* we don't care if someone yielded */
-		cq->state = MLX4_EN_CQ_STATE_NAPI;
-	spin_unlock(&cq->poll_lock);
-	return rc;
-}
-
-/* returns true is someone tried to get the cq while napi had it */
-static inline bool mlx4_en_cq_unlock_napi(struct mlx4_en_cq *cq)
-{
-	int rc = false;
-	spin_lock(&cq->poll_lock);
-	WARN_ON(cq->state & (MLX4_EN_CQ_STATE_POLL |
-			       MLX4_EN_CQ_STATE_NAPI_YIELD));
-
-	if (cq->state & MLX4_EN_CQ_STATE_POLL_YIELD)
-		rc = true;
-	cq->state = MLX4_EN_CQ_STATE_IDLE;
-	spin_unlock(&cq->poll_lock);
-	return rc;
-}
-
-/* called from mlx4_en_low_latency_recv(), BH are disabled */
-static inline bool mlx4_en_cq_lock_poll(struct mlx4_en_cq *cq)
-{
-	int rc = true;
-
-	spin_lock(&cq->poll_lock);
-	if ((cq->state & MLX4_CQ_LOCKED)) {
-		struct net_device *dev = cq->dev;
-		struct mlx4_en_priv *priv = netdev_priv(dev);
-		struct mlx4_en_rx_ring *rx_ring = priv->rx_ring[cq->ring];
-
-		cq->state |= MLX4_EN_CQ_STATE_POLL_YIELD;
-		rc = false;
-		rx_ring->yields++;
-	} else
-		/* preserve yield marks */
-		cq->state |= MLX4_EN_CQ_STATE_POLL;
-	spin_unlock(&cq->poll_lock);
-	return rc;
-}
-
-/* returns true if someone tried to get the cq while it was locked */
-static inline bool mlx4_en_cq_unlock_poll(struct mlx4_en_cq *cq)
-{
-	int rc = false;
-
-	spin_lock(&cq->poll_lock);
-	WARN_ON(cq->state & (MLX4_EN_CQ_STATE_NAPI));
-
-	if (cq->state & MLX4_EN_CQ_STATE_POLL_YIELD)
-		rc = true;
-	cq->state = MLX4_EN_CQ_STATE_IDLE;
-	spin_unlock(&cq->poll_lock);
-	return rc;
-}
-
-/* true if a socket is polling, even if it did not get the lock */
-static inline bool mlx4_en_cq_busy_polling(struct mlx4_en_cq *cq)
-{
-	WARN_ON(!(cq->state & MLX4_CQ_LOCKED));
-	return cq->state & CQ_USER_PEND;
-}
-#else
-static inline void mlx4_en_cq_init_lock(struct mlx4_en_cq *cq)
-{
-}
-
-static inline bool mlx4_en_cq_lock_napi(struct mlx4_en_cq *cq)
-{
-	return true;
-}
-
-static inline bool mlx4_en_cq_unlock_napi(struct mlx4_en_cq *cq)
-{
-	return false;
-}
-
-static inline bool mlx4_en_cq_lock_poll(struct mlx4_en_cq *cq)
-{
-	return false;
-}
-
-static inline bool mlx4_en_cq_unlock_poll(struct mlx4_en_cq *cq)
-{
-	return false;
-}
-
-static inline bool mlx4_en_cq_busy_polling(struct mlx4_en_cq *cq)
-{
-	return false;
-}
-#endif /* CONFIG_NET_RX_BUSY_POLL */
-
 #define MLX4_EN_WOL_DO_MODIFY (1ULL << 63)
 
 void mlx4_en_update_loopback_state(struct net_device *dev,