e1000: Maybe stop TX if not enough free descriptors
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index a1f5b06..e8a7608 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -2899,6 +2899,35 @@
return 0;
}
+static int __e1000_maybe_stop_tx(struct net_device *netdev, int size)
+{
+ struct e1000_adapter *adapter = netdev_priv(netdev);
+ struct e1000_tx_ring *tx_ring = adapter->tx_ring;
+
+ netif_stop_queue(netdev);
+ /* Herbert's original patch had:
+ * smp_mb__after_netif_stop_queue();
+ * but since that doesn't exist yet, just open code it. */
+ smp_mb();
+
+ /* We need to check again in a case another CPU has just
+ * made room available. */
+ if (likely(E1000_DESC_UNUSED(tx_ring) < size))
+ return -EBUSY;
+
+ /* A reprieve! */
+ netif_start_queue(netdev);
+ return 0;
+}
+
+static int e1000_maybe_stop_tx(struct net_device *netdev,
+ struct e1000_tx_ring *tx_ring, int size)
+{
+ if (likely(E1000_DESC_UNUSED(tx_ring) >= size))
+ return 0;
+ return __e1000_maybe_stop_tx(netdev, size);
+}
+
#define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1 )
static int
e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
@@ -2917,6 +2946,10 @@
unsigned int f;
len -= skb->data_len;
+ /* This goes back to the question of how to logically map a tx queue
+ * to a flow. Right now, performance is impacted slightly negatively
+ * if using multiple tx queues. If the stack breaks away from a
+ * single qdisc implementation, we can look at this again. */
tx_ring = adapter->tx_ring;
if (unlikely(skb->len <= 0)) {
@@ -3012,8 +3045,7 @@
/* need: count + 2 desc gap to keep tail from touching
* head, otherwise try next time */
- if (unlikely(E1000_DESC_UNUSED(tx_ring) < count + 2)) {
- netif_stop_queue(netdev);
+ if (unlikely(e1000_maybe_stop_tx(netdev, tx_ring, count + 2))) {
spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
return NETDEV_TX_BUSY;
}
@@ -3060,8 +3092,7 @@
netdev->trans_start = jiffies;
/* Make sure there is space in the ring for the next send. */
- if (unlikely(E1000_DESC_UNUSED(tx_ring) < MAX_SKB_FRAGS + 2))
- netif_stop_queue(netdev);
+ e1000_maybe_stop_tx(netdev, tx_ring, MAX_SKB_FRAGS + 2);
spin_unlock_irqrestore(&tx_ring->tx_lock, flags);
return NETDEV_TX_OK;
@@ -3556,13 +3587,14 @@
tx_ring->next_to_clean = i;
#define TX_WAKE_THRESHOLD 32
- if (unlikely(cleaned && netif_queue_stopped(netdev) &&
- netif_carrier_ok(netdev))) {
- spin_lock(&tx_ring->tx_lock);
- if (netif_queue_stopped(netdev) &&
- (E1000_DESC_UNUSED(tx_ring) >= TX_WAKE_THRESHOLD))
+ if (unlikely(cleaned && netif_carrier_ok(netdev) &&
+ E1000_DESC_UNUSED(tx_ring) >= TX_WAKE_THRESHOLD)) {
+ /* Make sure that anybody stopping the queue after this
+ * sees the new next_to_clean.
+ */
+ smp_mb();
+ if (netif_queue_stopped(netdev))
netif_wake_queue(netdev);
- spin_unlock(&tx_ring->tx_lock);
}
if (adapter->detect_tx_hung) {