From 9a1654ba0b50402a6bd03c7b0fe9b0200a5ea7b1 Mon Sep 17 00:00:00 2001 From: Jarek Poplawski Date: Sun, 15 Nov 2009 07:20:12 +0000 Subject: net: Optimize hard_start_xmit() return checking Recent changes in the TX error propagation require additional checking and masking of values returned from hard_start_xmit(), mainly to separate cases where skb was consumed. This aim can be simplified by changing the order of NETDEV_TX and NET_XMIT codes, because the latter are treated similarly to negative (ERRNO) values. After this change much simpler dev_xmit_complete() is also used in sch_direct_xmit(), so it is moved to netdevice.h. Additionally NET_RX definitions in netdevice.h are moved up from between TX codes to avoid confusion while reading the TX comment. Signed-off-by: Jarek Poplawski Signed-off-by: David S. Miller --- include/linux/netdevice.h | 42 ++++++++++++++++++++++++++++++------------ net/core/dev.c | 17 ----------------- net/sched/sch_generic.c | 23 +++++------------------ 3 files changed, 35 insertions(+), 47 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 61425d0c6123..7043f85e643d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -63,6 +63,10 @@ struct wireless_dev; #define HAVE_FREE_NETDEV /* free_netdev() */ #define HAVE_NETDEV_PRIV /* netdev_priv() */ +/* Backlog congestion levels */ +#define NET_RX_SUCCESS 0 /* keep 'em coming, baby */ +#define NET_RX_DROP 1 /* packet dropped */ + /* * Transmit return codes: transmit return codes originate from three different * namespaces: @@ -82,14 +86,10 @@ struct wireless_dev; /* qdisc ->enqueue() return codes. */ #define NET_XMIT_SUCCESS 0x00 -#define NET_XMIT_DROP 0x10 /* skb dropped */ -#define NET_XMIT_CN 0x20 /* congestion notification */ -#define NET_XMIT_POLICED 0x30 /* skb is shot by police */ -#define NET_XMIT_MASK 0xf0 /* qdisc flags in net/sch_generic.h */ - -/* Backlog congestion levels */ -#define NET_RX_SUCCESS 0 /* keep 'em coming, baby */ -#define NET_RX_DROP 1 /* packet dropped */ +#define NET_XMIT_DROP 0x01 /* skb dropped */ +#define NET_XMIT_CN 0x02 /* congestion notification */ +#define NET_XMIT_POLICED 0x03 /* skb is shot by police */ +#define NET_XMIT_MASK 0x0f /* qdisc flags in net/sch_generic.h */ /* NET_XMIT_CN is special. It does not guarantee that this packet is lost. It * indicates that the device will soon be dropping packets, or already drops @@ -98,16 +98,34 @@ struct wireless_dev; #define net_xmit_errno(e) ((e) != NET_XMIT_CN ? -ENOBUFS : 0) /* Driver transmit return codes */ -#define NETDEV_TX_MASK 0xf +#define NETDEV_TX_MASK 0xf0 enum netdev_tx { __NETDEV_TX_MIN = INT_MIN, /* make sure enum is signed */ - NETDEV_TX_OK = 0, /* driver took care of packet */ - NETDEV_TX_BUSY = 1, /* driver tx path was busy*/ - NETDEV_TX_LOCKED = 2, /* driver tx lock was already taken */ + NETDEV_TX_OK = 0x00, /* driver took care of packet */ + NETDEV_TX_BUSY = 0x10, /* driver tx path was busy*/ + NETDEV_TX_LOCKED = 0x20, /* driver tx lock was already taken */ }; typedef enum netdev_tx netdev_tx_t; +/* + * Current order: NETDEV_TX_MASK > NET_XMIT_MASK >= 0 is significant; + * hard_start_xmit() return < NET_XMIT_MASK means skb was consumed. + */ +static inline bool dev_xmit_complete(int rc) +{ + /* + * Positive cases with an skb consumed by a driver: + * - successful transmission (rc == NETDEV_TX_OK) + * - error while transmitting (rc < 0) + * - error while queueing to a different device (rc & NET_XMIT_MASK) + */ + if (likely(rc < NET_XMIT_MASK)) + return true; + + return false; +} + #endif #define MAX_ADDR_LEN 32 /* Largest hardware address length */ diff --git a/net/core/dev.c b/net/core/dev.c index 32045df1da5c..4b24d79414e3 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1924,23 +1924,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, return rc; } -static inline bool dev_xmit_complete(int rc) -{ - /* successful transmission */ - if (rc == NETDEV_TX_OK) - return true; - - /* error while transmitting, driver consumed skb */ - if (rc < 0) - return true; - - /* error while queueing to a different device, driver consumed skb */ - if (rc & NET_XMIT_MASK) - return true; - - return false; -} - /** * dev_queue_xmit - transmit a buffer * @skb: buffer to transmit diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index b13821ad2fb6..5173c1e1b19c 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -119,39 +119,26 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q, spin_unlock(root_lock); HARD_TX_LOCK(dev, txq, smp_processor_id()); - if (!netif_tx_queue_stopped(txq) && - !netif_tx_queue_frozen(txq)) { + if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq)) ret = dev_hard_start_xmit(skb, dev, txq); - /* an error implies that the skb was consumed */ - if (ret < 0) - ret = NETDEV_TX_OK; - /* all NET_XMIT codes map to NETDEV_TX_OK */ - ret &= ~NET_XMIT_MASK; - } HARD_TX_UNLOCK(dev, txq); spin_lock(root_lock); - switch (ret) { - case NETDEV_TX_OK: - /* Driver sent out skb successfully */ + if (dev_xmit_complete(ret)) { + /* Driver sent out skb successfully or skb was consumed */ ret = qdisc_qlen(q); - break; - - case NETDEV_TX_LOCKED: + } else if (ret == NETDEV_TX_LOCKED) { /* Driver try lock failed */ ret = handle_dev_cpu_collision(skb, txq, q); - break; - - default: + } else { /* Driver returned NETDEV_TX_BUSY - requeue skb */ if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit())) printk(KERN_WARNING "BUG %s code %d qlen %d\n", dev->name, ret, q->q.qlen); ret = dev_requeue_skb(skb, q); - break; } if (ret && (netif_tx_queue_stopped(txq) || -- cgit v1.2.3