Commit fcbeb976 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: introduce netdevice gso_min_segs attribute 



Some TSO engines might have a too heavy setup cost, that impacts
performance on hosts sending small bursts (2 MSS per packet).

This patch adds a device gso_min_segs, allowing drivers to set
a minimum segment size for TSO packets, according to the NIC
performance.

Tested on a mlx4 NIC, this allows to get a ~110% increase of
throughput when sending 2 MSS per packet.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9d31a7b9

include/linux/netdevice.h

+3 −1
Original line number Diff line number Diff line
@@ -1416,6 +1416,8 @@ enum netdev_priv_flags { 
 *	@gso_max_size:	Maximum size of generic segmentation offload

 *	@gso_max_segs:	Maximum number of segments that can be passed to the

 *			NIC for GSO

 *	@gso_min_segs:	Minimum number of segments that can be passed to the

 *			NIC for GSO

 *

 *	@dcbnl_ops:	Data Center Bridging netlink ops

 *	@num_tc:	Number of traffic classes in the net device
@@ -1666,7 +1668,7 @@ struct net_device { 
	unsigned int		gso_max_size;

#define GSO_MAX_SEGS		65535

	u16			gso_max_segs;



	u16			gso_min_segs;

#ifdef CONFIG_DCB

	const struct dcbnl_rtnl_ops *dcbnl_ops;

#endif

net/core/dev.c

+6 −3
Original line number Diff line number Diff line
@@ -2567,10 +2567,12 @@ static netdev_features_t harmonize_features(struct sk_buff *skb, 


netdev_features_t netif_skb_features(struct sk_buff *skb)

{

	const struct net_device *dev = skb->dev;

	netdev_features_t features = dev->features;

	u16 gso_segs = skb_shinfo(skb)->gso_segs;

	__be16 protocol = skb->protocol;

	netdev_features_t features = skb->dev->features;



	if (skb_shinfo(skb)->gso_segs > skb->dev->gso_max_segs)

	if (gso_segs > dev->gso_max_segs || gso_segs < dev->gso_min_segs)

		features &= ~NETIF_F_GSO_MASK;



	if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD)) {
@@ -2581,7 +2583,7 @@ netdev_features_t netif_skb_features(struct sk_buff *skb) 
	}



	features = netdev_intersect_features(features,

					     skb->dev->vlan_features |

					     dev->vlan_features |

					     NETIF_F_HW_VLAN_CTAG_TX |

					     NETIF_F_HW_VLAN_STAG_TX);
@@ -6661,6 +6663,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, 


	dev->gso_max_size = GSO_MAX_SIZE;

	dev->gso_max_segs = GSO_MAX_SEGS;

	dev->gso_min_segs = 0;



	INIT_LIST_HEAD(&dev->napi_list);

	INIT_LIST_HEAD(&dev->unreg_list);

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