[PATCH] Fix Tsi108 ethernet driver performance

[Alexandre Bounine]

From: Alexandre Bounine <alexandreb at tundra.com>

This patch improves performance of the Tsi108 Ethernet driver by
changing interrupt handling
for frame receive path. It reduces number of interrupts generated for
received frames and therefore lowers CPU utilization by the device
driver.
   
Signed-off-by: Alexandre Bounine <alexandreb at tundra.com>

---

diff -Nurp linux-2.6.22-hpc2/drivers/net/tsi108_eth.c
linux-2.6.22-tun/drivers/net/tsi108_eth.c
--- linux-2.6.22-hpc2/drivers/net/tsi108_eth.c	2007-07-08
19:32:17.000000000 -0400
+++ linux-2.6.22-tun/drivers/net/tsi108_eth.c	2007-07-12
16:55:50.000000000 -0400
@@ -58,6 +58,7 @@
 #define MII_READ_DELAY 10000	/* max link wait time in msec */
 
 #define TSI108_RXRING_LEN     256
+#define TSI108_RX_INT_FREQ    32
 
 /* NOTE: The driver currently does not support receiving packets
  * larger than the buffer size, so don't decrease this (unless you
@@ -69,8 +70,10 @@
 
 #define TSI108_TX_INT_FREQ    64
 
-/* Check the phy status every half a second. */
-#define CHECK_PHY_INTERVAL (HZ/2)
+/* Timer interval to check the RX queue status */
+#define CHECK_RX_INTERVAL	(HZ/50)
+/* Timer interval to check the PHY status */
+#define CHECK_PHY_INTERVAL	(CHECK_RX_INTERVAL * 10)
 
 static int tsi108_init_one(struct platform_device *pdev);
 static int tsi108_ether_remove(struct platform_device *pdev);
@@ -104,6 +107,7 @@ struct tsi108_prv_data {
 	unsigned int txfree;
 
 	unsigned int phy_ok;		/* The PHY is currently powered
on. */
+	unsigned int phy_chk_count;
 
 	/* PHY status (duplex is 1 for half, 2 for full,
 	 * so that the default 0 indicates that neither has
@@ -823,7 +827,10 @@ static int tsi108_refill_rx(struct net_d
 		 */
 
 		data->rxring[rx].blen = TSI108_RX_SKB_SIZE;
-		data->rxring[rx].misc = TSI108_RX_OWN | TSI108_RX_INT;
+		if (rx % TSI108_RX_INT_FREQ)
+			data->rxring[rx].misc = TSI108_RX_OWN;
+		else
+			data->rxring[rx].misc = TSI108_RX_OWN |
TSI108_RX_INT;
 
 		data->rxhead = (data->rxhead + 1) % TSI108_RXRING_LEN;
 		data->rxfree++;
@@ -973,24 +980,22 @@ static void tsi108_rx_int(struct net_dev
 	}
 }
 
-/* If the RX ring has run out of memory, try periodically
- * to allocate some more, as otherwise poll would never
- * get called (apart from the initial end-of-queue condition).
- *
- * This is called once per second (by default) from the thread.
+/* tsi108_check_rxring() is used to periodically check if the RX ring
has
+ * pending frames that have not been reported by RX interrupt (due to
interrupt
+ * moderation). It is called with CHECK_RX_INTERVAL timer interval.
  */
 
 static void tsi108_check_rxring(struct net_device *dev)
 {
 	struct tsi108_prv_data *data = netdev_priv(dev);
+	unsigned int rx = data->rxtail;
 
-	/* A poll is scheduled, as opposed to caling tsi108_refill_rx
-	 * directly, so as to keep the receive path single-threaded
-	 * (and thus not needing a lock).
-	 */
-
-	if (netif_running(dev) && data->rxfree < TSI108_RXRING_LEN / 4)
+	/* Schedule a poll (if required) */
+	if (netif_running(dev) &&
+	    0 == (data->rxring[rx].misc & TSI108_RX_OWN)) {
+		data->rxpending = 1;
 		tsi108_rx_int(dev);
+	}
 }
 
 static void tsi108_tx_int(struct net_device *dev)
@@ -1295,6 +1300,7 @@ static void tsi108_init_phy(struct net_d
 
 	printk(KERN_DEBUG "PHY_STAT reg contains %08x\n", phyval);
 	data->phy_ok = 1;
+	data->phy_chk_count = 0;
 	data->init_media = 1;
 	spin_unlock_irqrestore(&phy_lock, flags);
 }
@@ -1664,9 +1670,12 @@ static void tsi108_timed_checker(unsigne
 	struct net_device *dev = (struct net_device *)dev_ptr;
 	struct tsi108_prv_data *data = netdev_priv(dev);
 
-	tsi108_check_phy(dev);
+	/* We assume that RX queue is checked more often than PHY status
*/
+	if (data->phy_chk_count++ == 0)
+		tsi108_check_phy(dev);
 	tsi108_check_rxring(dev);
-	mod_timer(&data->timer, jiffies + CHECK_PHY_INTERVAL);
+	data->phy_chk_count %= (CHECK_PHY_INTERVAL/CHECK_RX_INTERVAL);
+	mod_timer(&data->timer, jiffies + CHECK_RX_INTERVAL);
 }
 
 static int tsi108_ether_init(void)


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