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Message-ID: <20091115172012.GA2976@ami.dom.local>
Date: Sun, 15 Nov 2009 18:20:12 +0100
From: Jarek Poplawski <jarkao2@...il.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Linux Netdev List <netdev@...r.kernel.org>,
Patrick McHardy <kaber@...sh.net>
Subject: [PATCH net-next] 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 <jarkao2@...il.com>
---
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 61425d0..7043f85 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 548340b..67669c4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1909,23 +1909,6 @@ 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 b13821a..5173c1e 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) ||
--
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