Patchwork [7/9] sky2: skb recycling

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Submitter stephen hemminger
Date June 17, 2009, 5:30 p.m.
Message ID <20090617173140.244124173@vyatta.com>
Download mbox | patch
Permalink /patch/28799/
State Accepted
Delegated to: David Miller
Headers show

Comments

stephen hemminger - June 17, 2009, 5:30 p.m.
This patch implements skb recycling. It reclaims transmitted skb's
for use in the receive ring.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
David Miller - June 18, 2009, 1:51 a.m.
From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 17 Jun 2009 10:30:38 -0700

> This patch implements skb recycling. It reclaims transmitted skb's
> for use in the receive ring.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Applied.
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Jesse Brandeburg - June 18, 2009, 9:13 p.m.
On Wed, 17 Jun 2009, Stephen Hemminger wrote:

> This patch implements skb recycling. It reclaims transmitted skb's
> for use in the receive ring.

Was sky2 able to show any gain in forwarding performance due to this 
patch?  Was it significant?  What kind of machine was used to test?
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stephen hemminger - June 18, 2009, 9:22 p.m.
On Thu, 18 Jun 2009 14:13:20 -0700 (Pacific Daylight Time)
"Brandeburg, Jesse" <jesse.brandeburg@intel.com> wrote:

> 
> 
> On Wed, 17 Jun 2009, Stephen Hemminger wrote:
> 
> > This patch implements skb recycling. It reclaims transmitted skb's
> > for use in the receive ring.
> 
> Was sky2 able to show any gain in forwarding performance due to this 
> patch?  Was it significant?  What kind of machine was used to test?

no not really, sky2 has other issue which hurt performance.

Patch

--- a/drivers/net/sky2.c	2009-06-17 10:29:57.400008862 -0700
+++ b/drivers/net/sky2.c	2009-06-17 10:29:58.250810500 -0700
@@ -1176,6 +1176,7 @@  static void sky2_rx_clean(struct sky2_po
 			re->skb = NULL;
 		}
 	}
+	skb_queue_purge(&sky2->rx_recycle);
 }
 
 /* Basic MII support */
@@ -1252,6 +1253,12 @@  static void sky2_vlan_rx_register(struct
 }
 #endif
 
+/* Amount of required worst case padding in rx buffer */
+static inline unsigned sky2_rx_pad(const struct sky2_hw *hw)
+{
+	return (hw->flags & SKY2_HW_RAM_BUFFER) ? 8 : 2;
+}
+
 /*
  * Allocate an skb for receiving. If the MTU is large enough
  * make the skb non-linear with a fragment list of pages.
@@ -1261,6 +1268,13 @@  static struct sk_buff *sky2_rx_alloc(str
 	struct sk_buff *skb;
 	int i;
 
+	skb = __skb_dequeue(&sky2->rx_recycle);
+	if (!skb)
+		skb = netdev_alloc_skb(sky2->netdev, sky2->rx_data_size
+				       + sky2_rx_pad(sky2->hw));
+	if (!skb)
+		goto nomem;
+
 	if (sky2->hw->flags & SKY2_HW_RAM_BUFFER) {
 		unsigned char *start;
 		/*
@@ -1269,18 +1283,10 @@  static struct sk_buff *sky2_rx_alloc(str
 		 * The buffer returned from netdev_alloc_skb is
 		 * aligned except if slab debugging is enabled.
 		 */
-		skb = netdev_alloc_skb(sky2->netdev, sky2->rx_data_size + 8);
-		if (!skb)
-			goto nomem;
 		start = PTR_ALIGN(skb->data, 8);
 		skb_reserve(skb, start - skb->data);
-	} else {
-		skb = netdev_alloc_skb(sky2->netdev,
-				       sky2->rx_data_size + NET_IP_ALIGN);
-		if (!skb)
-			goto nomem;
+	} else
 		skb_reserve(skb, NET_IP_ALIGN);
-	}
 
 	for (i = 0; i < sky2->rx_nfrags; i++) {
 		struct page *page = alloc_page(GFP_ATOMIC);
@@ -1357,6 +1363,8 @@  static int sky2_rx_start(struct sky2_por
 
 	sky2->rx_data_size = size;
 
+	skb_queue_head_init(&sky2->rx_recycle);
+
 	/* Fill Rx ring */
 	for (i = 0; i < sky2->rx_pending; i++) {
 		re = sky2->rx_ring + i;
@@ -1764,14 +1772,22 @@  static void sky2_tx_complete(struct sky2
 		}
 
 		if (le->ctrl & EOP) {
+			struct sk_buff *skb = re->skb;
+
 			if (unlikely(netif_msg_tx_done(sky2)))
 				printk(KERN_DEBUG "%s: tx done %u\n",
 				       dev->name, idx);
 
 			dev->stats.tx_packets++;
-			dev->stats.tx_bytes += re->skb->len;
+			dev->stats.tx_bytes += skb->len;
+
+			if (skb_queue_len(&sky2->rx_recycle) < sky2->rx_pending
+			    && skb_recycle_check(skb, sky2->rx_data_size
+						 + sky2_rx_pad(sky2->hw)))
+				__skb_queue_head(&sky2->rx_recycle, skb);
+			else
+				dev_kfree_skb_any(skb);
 
-			dev_kfree_skb_any(re->skb);
 			sky2->tx_next = RING_NEXT(idx, TX_RING_SIZE);
 		}
 	}
--- a/drivers/net/sky2.h	2009-06-17 10:29:17.200758602 -0700
+++ b/drivers/net/sky2.h	2009-06-17 10:29:58.252811835 -0700
@@ -2028,6 +2028,7 @@  struct sky2_port {
 	u16		     rx_pending;
 	u16		     rx_data_size;
 	u16		     rx_nfrags;
+	struct sk_buff_head  rx_recycle;
 
 #ifdef SKY2_VLAN_TAG_USED
 	u16		     rx_tag;