[dpdk-dev] [PATCH] net/mlx: remove link update lock

[Olivier Matz]

From: Matthieu Ternisien d'Ouville <matthieu.tdo at 6wind.com>

Retrieving link status information through the link update callback should
be quick and non-blocking.

Mellanox PMDs retrieve this information through ioctl() calls on the
related kernel netdevice. This appears to take a long time to
complete and may cause significant slowdowns in applications.

While these system calls cannot be accelerated, removing the lock on the
private structure allows applications to perform other control operations
from separate threads in the meantime. This function remains safe without
locking as it does not write the private structure, it is only used to
retrieve the name of the netdevice.

Signed-off-by: Matthieu Ternisien d'Ouville <matthieu.tdo at 6wind.com>
Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
---
 drivers/net/mlx4/mlx4.c        | 32 ++++++--------------------------
 drivers/net/mlx5/mlx5.c        |  2 +-
 drivers/net/mlx5/mlx5.h        |  1 -
 drivers/net/mlx5/mlx5_ethdev.c | 30 ++++++------------------------
 4 files changed, 13 insertions(+), 52 deletions(-)

diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index eb06f56..941176c 100644
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -4823,7 +4823,7 @@ mlx4_allmulticast_disable(struct rte_eth_dev *dev)
 }
 
 /**
- * DPDK callback to retrieve physical link information (unlocked version).
+ * DPDK callback to retrieve physical link information.
  *
  * @param dev
  *   Pointer to Ethernet device structure.
@@ -4831,9 +4831,9 @@ mlx4_allmulticast_disable(struct rte_eth_dev *dev)
  *   Wait for request completion (ignored).
  */
 static int
-mlx4_link_update_unlocked(struct rte_eth_dev *dev, int wait_to_complete)
+mlx4_link_update(struct rte_eth_dev *dev, int wait_to_complete)
 {
-	struct priv *priv = mlx4_get_priv(dev);
+	const struct priv *priv = mlx4_get_priv(dev);
 	struct ethtool_cmd edata = {
 		.cmd = ETHTOOL_GSET
 	};
@@ -4841,6 +4841,8 @@ mlx4_link_update_unlocked(struct rte_eth_dev *dev, int wait_to_complete)
 	struct rte_eth_link dev_link;
 	int link_speed = 0;
 
+	/* priv_lock() is not taken to allow concurrent calls. */
+
 	if (priv == NULL)
 		return -EINVAL;
 	(void)wait_to_complete;
@@ -4876,28 +4878,6 @@ mlx4_link_update_unlocked(struct rte_eth_dev *dev, int wait_to_complete)
 }
 
 /**
- * DPDK callback to retrieve physical link information.
- *
- * @param dev
- *   Pointer to Ethernet device structure.
- * @param wait_to_complete
- *   Wait for request completion (ignored).
- */
-static int
-mlx4_link_update(struct rte_eth_dev *dev, int wait_to_complete)
-{
-	struct priv *priv = mlx4_get_priv(dev);
-	int ret;
-
-	if (priv == NULL)
-		return -EINVAL;
-	priv_lock(priv);
-	ret = mlx4_link_update_unlocked(dev, wait_to_complete);
-	priv_unlock(priv);
-	return ret;
-}
-
-/**
  * DPDK callback to change the MTU.
  *
  * Setting the MTU affects hardware MRU (packets larger than the MTU cannot be
@@ -5413,7 +5393,7 @@ priv_dev_link_status_handler(struct priv *priv, struct rte_eth_dev *dev)
 		struct rte_eth_link *link = &dev->data->dev_link;
 
 		priv->pending_alarm = 0;
-		mlx4_link_update_unlocked(dev, 0);
+		mlx4_link_update(dev, 0);
 		if (((link->link_speed == 0) && link->link_status) ||
 		    ((link->link_speed != 0) && !link->link_status)) {
 			/* Inconsistent status, check again later. */
diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index 6293c1f..d936e72 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -680,7 +680,7 @@ mlx5_pci_probe(struct rte_pci_driver *pci_drv, struct rte_pci_device *pci_dev)
 		/* Bring Ethernet device up. */
 		DEBUG("forcing Ethernet interface up");
 		priv_set_flags(priv, ~IFF_UP, IFF_UP);
-		mlx5_link_update_unlocked(priv->dev, 1);
+		mlx5_link_update(priv->dev, 1);
 		continue;
 
 port_error:
diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index ee62e04..d39b199 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -194,7 +194,6 @@ int priv_set_flags(struct priv *, unsigned int, unsigned int);
 int mlx5_dev_configure(struct rte_eth_dev *);
 void mlx5_dev_infos_get(struct rte_eth_dev *, struct rte_eth_dev_info *);
 const uint32_t *mlx5_dev_supported_ptypes_get(struct rte_eth_dev *dev);
-int mlx5_link_update_unlocked(struct rte_eth_dev *, int);
 int mlx5_link_update(struct rte_eth_dev *, int);
 int mlx5_dev_set_mtu(struct rte_eth_dev *, uint16_t);
 int mlx5_dev_get_flow_ctrl(struct rte_eth_dev *, struct rte_eth_fc_conf *);
diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index fbb1b65..a46526e 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -628,7 +628,7 @@ mlx5_dev_supported_ptypes_get(struct rte_eth_dev *dev)
 }
 
 /**
- * Retrieve physical link information (unlocked version using legacy ioctl).
+ * DPDK callback to retrieve physical link information.
  *
  * @param dev
  *   Pointer to Ethernet device structure.
@@ -646,6 +646,8 @@ mlx5_link_update_unlocked_gset(struct rte_eth_dev *dev, int wait_to_complete)
 	struct rte_eth_link dev_link;
 	int link_speed = 0;
 
+	/* priv_lock() is not taken to allow concurrent calls. */
+
 	(void)wait_to_complete;
 	if (priv_ifreq(priv, SIOCGIFFLAGS, &ifr)) {
 		WARN("ioctl(SIOCGIFFLAGS) failed: %s", strerror(errno));
@@ -790,7 +792,7 @@ mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int wait_to_complete)
 }
 
 /**
- * DPDK callback to retrieve physical link information (unlocked version).
+ * DPDK callback to retrieve physical link information.
  *
  * @param dev
  *   Pointer to Ethernet device structure.
@@ -798,7 +800,7 @@ mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int wait_to_complete)
  *   Wait for request completion (ignored).
  */
 int
-mlx5_link_update_unlocked(struct rte_eth_dev *dev, int wait_to_complete)
+mlx5_link_update(struct rte_eth_dev *dev, int wait_to_complete)
 {
 	int ret;
 
@@ -809,26 +811,6 @@ mlx5_link_update_unlocked(struct rte_eth_dev *dev, int wait_to_complete)
 }
 
 /**
- * DPDK callback to retrieve physical link information.
- *
- * @param dev
- *   Pointer to Ethernet device structure.
- * @param wait_to_complete
- *   Wait for request completion (ignored).
- */
-int
-mlx5_link_update(struct rte_eth_dev *dev, int wait_to_complete)
-{
-	struct priv *priv = mlx5_get_priv(dev);
-	int ret;
-
-	priv_lock(priv);
-	ret = mlx5_link_update_unlocked(dev, wait_to_complete);
-	priv_unlock(priv);
-	return ret;
-}
-
-/**
  * DPDK callback to change the MTU.
  *
  * Setting the MTU affects hardware MRU (packets larger than the MTU cannot be
@@ -1164,7 +1146,7 @@ priv_dev_link_status_handler(struct priv *priv, struct rte_eth_dev *dev)
 		struct rte_eth_link *link = &dev->data->dev_link;
 
 		priv->pending_alarm = 0;
-		mlx5_link_update_unlocked(dev, 0);
+		mlx5_link_update(dev, 0);
 		if (((link->link_speed == 0) && link->link_status) ||
 		    ((link->link_speed != 0) && !link->link_status)) {
 			/* Inconsistent status, check again later. */
-- 
2.8.1