From 43279500decad66ccdddacae7948a1d23be1bef6 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 27 Mar 2014 16:38:30 +0100 Subject: [PATCH] packet: respect devices with LLTX flag in direct xmit Quite often it can be useful to test with dummy or similar devices as a blackhole sink for skbs. Such devices are only equipped with a single txq, but marked as NETIF_F_LLTX as they do not require locking their internal queues on xmit (or implement locking themselves). Therefore, rather use HARD_TX_{UN,}LOCK API, so that NETIF_F_LLTX will be respected. trafgen mmap/TX_RING example against dummy device with config foo: { fill(0xff, 64) } results in the following performance improvements for such scenarios on an ordinary Core i7/2.80GHz: Before: Performance counter stats for 'trafgen -i foo -o du0 -n100000000' (10 runs): 160,975,944,159 instructions:k # 0.55 insns per cycle ( +- 0.09% ) 293,319,390,278 cycles:k # 0.000 GHz ( +- 0.35% ) 192,501,104 branch-misses:k ( +- 1.63% ) 831 context-switches:k ( +- 9.18% ) 7 cpu-migrations:k ( +- 7.40% ) 69,382 cache-misses:k # 0.010 % of all cache refs ( +- 2.18% ) 671,552,021 cache-references:k ( +- 1.29% ) 22.856401569 seconds time elapsed ( +- 0.33% ) After: Performance counter stats for 'trafgen -i foo -o du0 -n100000000' (10 runs): 133,788,739,692 instructions:k # 0.92 insns per cycle ( +- 0.06% ) 145,853,213,256 cycles:k # 0.000 GHz ( +- 0.17% ) 59,867,100 branch-misses:k ( +- 4.72% ) 384 context-switches:k ( +- 3.76% ) 6 cpu-migrations:k ( +- 6.28% ) 70,304 cache-misses:k # 0.077 % of all cache refs ( +- 1.73% ) 90,879,408 cache-references:k ( +- 1.35% ) 11.719372413 seconds time elapsed ( +- 0.24% ) Signed-off-by: Daniel Borkmann Cc: Jesper Dangaard Brouer Signed-off-by: David S. Miller --- net/packet/af_packet.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 097a354ec8cd..01039d2b1695 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -243,40 +243,40 @@ static int packet_direct_xmit(struct sk_buff *skb) const struct net_device_ops *ops = dev->netdev_ops; netdev_features_t features; struct netdev_queue *txq; + int ret = NETDEV_TX_BUSY; u16 queue_map; - int ret; if (unlikely(!netif_running(dev) || - !netif_carrier_ok(dev))) { - kfree_skb(skb); - return NET_XMIT_DROP; - } + !netif_carrier_ok(dev))) + goto drop; features = netif_skb_features(skb); if (skb_needs_linearize(skb, features) && - __skb_linearize(skb)) { - kfree_skb(skb); - return NET_XMIT_DROP; - } + __skb_linearize(skb)) + goto drop; queue_map = skb_get_queue_mapping(skb); txq = netdev_get_tx_queue(dev, queue_map); - __netif_tx_lock_bh(txq); - if (unlikely(netif_xmit_frozen_or_stopped(txq))) { - ret = NETDEV_TX_BUSY; - kfree_skb(skb); - goto out; + local_bh_disable(); + + HARD_TX_LOCK(dev, txq, smp_processor_id()); + if (!netif_xmit_frozen_or_stopped(txq)) { + ret = ops->ndo_start_xmit(skb, dev); + if (ret == NETDEV_TX_OK) + txq_trans_update(txq); } + HARD_TX_UNLOCK(dev, txq); - ret = ops->ndo_start_xmit(skb, dev); - if (likely(dev_xmit_complete(ret))) - txq_trans_update(txq); - else + local_bh_enable(); + + if (!dev_xmit_complete(ret)) kfree_skb(skb); -out: - __netif_tx_unlock_bh(txq); + return ret; +drop: + kfree_skb(skb); + return NET_XMIT_DROP; } static struct net_device *packet_cached_dev_get(struct packet_sock *po) -- 2.30.2