[PATCH] s390: lcs performance enhancements

[patch 1/2] s390: lcs performance enhancements

From: Klaus Wacker <kdwacker@de.ibm.com>
	- When flood pinging (with large packet size) an LCS device,
	  about 90 % of all packets are dropped by driver.
	- increased number of lcs IO buffers to 32.
	- use netif_stop_queue/netif_wake_queue in lcs_start_xmit routine
	- don't lock the whole xmit routine but just the piece of code where
	  tx_buffer is touched.

Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>

diffstat:
 lcs.c |   31 +++++++++++++++++--------------
 lcs.h |    2 +-
 2 files changed, 18 insertions(+), 15 deletions(-)
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

2 files changed, 18 insertions, 15 deletions

diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 6229ba4995a..9cf88d7201d 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -98,9 +98,9 @@ lcs_register_debug_facility(void)
                 return -ENOMEM;
         }
         debug_register_view(lcs_dbf_setup, &debug_hex_ascii_view);
-        debug_set_level(lcs_dbf_setup, 4);
+        debug_set_level(lcs_dbf_setup, 2);
         debug_register_view(lcs_dbf_trace, &debug_hex_ascii_view);
-        debug_set_level(lcs_dbf_trace, 4);
+        debug_set_level(lcs_dbf_trace, 2);
         return 0;
 }
 
@@ -1292,9 +1292,8 @@ lcs_set_multicast_list(struct net_device *dev)
         LCS_DBF_TEXT(4, trace, "setmulti");
         card = (struct lcs_card *) dev->priv;
 
-        if (!lcs_set_thread_start_bit(card, LCS_SET_MC_THREAD)) {
+        if (!lcs_set_thread_start_bit(card, LCS_SET_MC_THREAD)) 
                 schedule_work(&card->kernel_thread_starter);
-        }
 }
 
 #endif /* CONFIG_IP_MULTICAST */
@@ -1459,6 +1458,8 @@ lcs_txbuffer_cb(struct lcs_channel *channel, struct lcs_buffer *buffer)
         lcs_release_buffer(channel, buffer);
         card = (struct lcs_card *)
                 ((char *) channel - offsetof(struct lcs_card, write));
+        if (netif_queue_stopped(card->dev))
+                netif_wake_queue(card->dev);
         spin_lock(&card->lock);
         card->tx_emitted--;
         if (card->tx_emitted <= 0 && card->tx_buffer != NULL)
@@ -1478,6 +1479,7 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
                  struct net_device *dev)
 {
         struct lcs_header *header;
+        int rc = 0;
 
         LCS_DBF_TEXT(5, trace, "hardxmit");
         if (skb == NULL) {
@@ -1492,10 +1494,8 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
                 card->stats.tx_carrier_errors++;
                 return 0;
         }
-        if (netif_queue_stopped(dev) ) {
-                card->stats.tx_dropped++;
-                return -EBUSY;
-        }
+        netif_stop_queue(card->dev);
+        spin_lock(&card->lock);
         if (card->tx_buffer != NULL &&
             card->tx_buffer->count + sizeof(struct lcs_header) +
             skb->len + sizeof(u16) > LCS_IOBUFFERSIZE)
@@ -1506,7 +1506,8 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
                 card->tx_buffer = lcs_get_buffer(&card->write);
                 if (card->tx_buffer == NULL) {
                         card->stats.tx_dropped++;
-                        return -EBUSY;
+                        rc = -EBUSY;
+                        goto out;
                 }
                 card->tx_buffer->callback = lcs_txbuffer_cb;
                 card->tx_buffer->count = 0;
@@ -1518,13 +1519,18 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
         header->type = card->lan_type;
         header->slot = card->portno;
         memcpy(header + 1, skb->data, skb->len);
+        spin_unlock(&card->lock);
         card->stats.tx_bytes += skb->len;
         card->stats.tx_packets++;
         dev_kfree_skb(skb);
-        if (card->tx_emitted <= 0)
+        netif_wake_queue(card->dev);
+        spin_lock(&card->lock);
+        if (card->tx_emitted <= 0 && card->tx_buffer != NULL)
                 /* If this is the first tx buffer emit it immediately. */
                 __lcs_emit_txbuffer(card);
-        return 0;
+out:
+        spin_unlock(&card->lock);
+        return rc;
 }
 
 static int
@@ -1535,9 +1541,7 @@ lcs_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
         LCS_DBF_TEXT(5, trace, "pktxmit");
         card = (struct lcs_card *) dev->priv;
-        spin_lock(&card->lock);
         rc = __lcs_start_xmit(card, skb, dev);
-        spin_unlock(&card->lock);
         return rc;
 }
 
@@ -2319,7 +2323,6 @@ __init lcs_init_module(void)
                 PRINT_ERR("Initialization failed\n");
                 return rc;
         }
-
         return 0;
 }
 
diff --git a/drivers/s390/net/lcs.h b/drivers/s390/net/lcs.h
index 08e60ad4391..2fad5e40c2e 100644
--- a/drivers/s390/net/lcs.h
+++ b/drivers/s390/net/lcs.h
@@ -95,7 +95,7 @@ do {                                       \
  */
 #define LCS_ILLEGAL_OFFSET              0xffff
 #define LCS_IOBUFFERSIZE                0x5000
-#define LCS_NUM_BUFFS                   8       /* needs to be power of 2 */
+#define LCS_NUM_BUFFS                   32      /* needs to be power of 2 */
 #define LCS_MAC_LENGTH                  6
 #define LCS_INVALID_PORT_NO             -1
 #define LCS_LANCMD_TIMEOUT_DEFAULT      5