net: fs_enet: Add NAPI TX
When using a MPC8xx as a router, 'perf' shows a significant time spent in
fs_enet_interrupt() and fs_enet_start_xmit().
'perf annotate' shows that the time spent in fs_enet_start_xmit is indeed spent
between spin_unlock_irqrestore() and the following instruction, hence in
interrupt handling. This is due to the TX complete interrupt that fires after
each transmitted packet.
This patch modifies the handling of TX complete to use NAPI.
With this patch, my NAT router offers a throughput improved by 21%
Original performance:
[root@localhost tmp]# scp toto pgs:/tmp
toto 100% 256MB 2.8MB/s 01:31
Performance with the patch:
[root@localhost tmp]# scp toto pgs:/tmp
toto 100% 256MB 3.4MB/s 01:16
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
index 71a25b4..c92c3b7 100644
--- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
+++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
@@ -215,17 +215,23 @@
return received;
}
-static void fs_enet_tx(struct net_device *dev)
+static int fs_enet_tx_napi(struct napi_struct *napi, int budget)
{
- struct fs_enet_private *fep = netdev_priv(dev);
+ struct fs_enet_private *fep = container_of(napi, struct fs_enet_private,
+ napi_tx);
+ struct net_device *dev = fep->ndev;
cbd_t __iomem *bdp;
struct sk_buff *skb;
int dirtyidx, do_wake, do_restart;
u16 sc;
+ int has_tx_work = 0;
spin_lock(&fep->tx_lock);
bdp = fep->dirty_tx;
+ /* clear TX status bits for napi*/
+ (*fep->ops->napi_clear_tx_event)(dev);
+
do_wake = do_restart = 0;
while (((sc = CBDR_SC(bdp)) & BD_ENET_TX_READY) == 0) {
dirtyidx = bdp - fep->tx_bd_base;
@@ -278,7 +284,7 @@
/*
* Free the sk buffer associated with this last transmit.
*/
- dev_kfree_skb_irq(skb);
+ dev_kfree_skb(skb);
fep->tx_skbuff[dirtyidx] = NULL;
/*
@@ -295,6 +301,7 @@
*/
if (!fep->tx_free++)
do_wake = 1;
+ has_tx_work = 1;
}
fep->dirty_tx = bdp;
@@ -302,10 +309,19 @@
if (do_restart)
(*fep->ops->tx_restart)(dev);
+ if (!has_tx_work) {
+ napi_complete(napi);
+ (*fep->ops->napi_enable_tx)(dev);
+ }
+
spin_unlock(&fep->tx_lock);
if (do_wake)
netif_wake_queue(dev);
+
+ if (has_tx_work)
+ return budget;
+ return 0;
}
/*
@@ -350,8 +366,17 @@
__napi_schedule(&fep->napi);
}
- if (int_events & fep->ev_tx)
- fs_enet_tx(dev);
+ if (int_events & fep->ev_tx) {
+ napi_ok = napi_schedule_prep(&fep->napi_tx);
+
+ (*fep->ops->napi_disable_tx)(dev);
+ (*fep->ops->clear_int_events)(dev, fep->ev_napi_tx);
+
+ /* NOTE: it is possible for FCCs in NAPI mode */
+ /* to submit a spurious interrupt while in poll */
+ if (napi_ok)
+ __napi_schedule(&fep->napi_tx);
+ }
}
handled = nr > 0;
@@ -484,7 +509,6 @@
cbd_t __iomem *bdp;
int curidx;
u16 sc;
- unsigned long flags;
#ifdef CONFIG_FS_ENET_MPC5121_FEC
if (((unsigned long)skb->data) & 0x3) {
@@ -499,7 +523,7 @@
}
}
#endif
- spin_lock_irqsave(&fep->tx_lock, flags);
+ spin_lock(&fep->tx_lock);
/*
* Fill in a Tx ring entry
@@ -508,7 +532,7 @@
if (!fep->tx_free || (CBDR_SC(bdp) & BD_ENET_TX_READY)) {
netif_stop_queue(dev);
- spin_unlock_irqrestore(&fep->tx_lock, flags);
+ spin_unlock(&fep->tx_lock);
/*
* Ooops. All transmit buffers are full. Bail out.
@@ -564,7 +588,7 @@
(*fep->ops->tx_kickstart)(dev);
- spin_unlock_irqrestore(&fep->tx_lock, flags);
+ spin_unlock(&fep->tx_lock);
return NETDEV_TX_OK;
}
@@ -685,6 +709,7 @@
fs_init_bds(fep->ndev);
napi_enable(&fep->napi);
+ napi_enable(&fep->napi_tx);
/* Install our interrupt handler. */
r = request_irq(fep->interrupt, fs_enet_interrupt, IRQF_SHARED,
@@ -692,6 +717,7 @@
if (r != 0) {
dev_err(fep->dev, "Could not allocate FS_ENET IRQ!");
napi_disable(&fep->napi);
+ napi_disable(&fep->napi_tx);
return -EINVAL;
}
@@ -699,6 +725,7 @@
if (err) {
free_irq(fep->interrupt, dev);
napi_disable(&fep->napi);
+ napi_disable(&fep->napi_tx);
return err;
}
phy_start(fep->phydev);
@@ -716,6 +743,7 @@
netif_stop_queue(dev);
netif_carrier_off(dev);
napi_disable(&fep->napi);
+ napi_disable(&fep->napi_tx);
phy_stop(fep->phydev);
spin_lock_irqsave(&fep->lock, flags);
@@ -971,6 +999,7 @@
ndev->netdev_ops = &fs_enet_netdev_ops;
ndev->watchdog_timeo = 2 * HZ;
netif_napi_add(ndev, &fep->napi, fs_enet_rx_napi, fpi->napi_weight);
+ netif_napi_add(ndev, &fep->napi_tx, fs_enet_tx_napi, 2);
ndev->ethtool_ops = &fs_ethtool_ops;