Jeff Kirsher a écrit :
- This patch is to improve performance by adding prefetch to the ixgb driver
- Add driver comments
Signed-off-by: Jeff Kirsher <[EMAIL PROTECTED]>
Signed-off-by: Jesse Brandeburg <[EMAIL PROTECTED]>
Signed-off-by: John Ronciak <[EMAIL PROTECTED]>
---
drivers/net/ixgb/ixgb_main.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
index 26cb0d5..98303cb 100644
--- a/drivers/net/ixgb/ixgb_main.c
+++ b/drivers/net/ixgb/ixgb_main.c
@@ -29,6 +29,13 @@
#include "ixgb.h"
/* Change Log
+ * 1.0.104 10-Jan-2006
+ * - fix for copybreak/recycle
+ * 1.0.103 Oct-3
+ * - suck in some e1000 changes, including copybreak and LLTX
+ * - support for CX4 adapters
+ * 1.0.102 June-20-2005
+ * - add a workaround for a hardware issue when using TSO
* 1.0.96 04/19/05
* - Make needlessly global code static -- [EMAIL PROTECTED]
* - ethtool cleanup -- [EMAIL PROTECTED]
@@ -1916,7 +1923,7 @@ ixgb_clean_rx_irq(struct ixgb_adapter *a
skb = buffer_info->skb;
buffer_info->skb = NULL;
- prefetch(skb->data);
+ prefetch(skb->data - NET_IP_ALIGN);
I doubt this change is usefull.
skb->data and dkb->dta - NET_IP_ALIGN are on the same cache line.
So prefetch(skb->data) is cheaper for he compiler and has the same effect on
the memory prefetch that is eventually done by the cpu.
if(++i == rx_ring->count) i = 0;
next_rxd = IXGB_RX_DESC(*rx_ring, i);
@@ -1929,6 +1936,7 @@ ixgb_clean_rx_irq(struct ixgb_adapter *a
next_buffer = &rx_ring->buffer_info[i];
next_skb = next_buffer->skb;
prefetch(next_skb);
+ prefetch(next_skb->data - NET_IP_ALIGN);
I doubt that next->skb_data is available for free just after a
prefetch(next_skb). This second prefetch has a hidden cost : The memory
location (&next_skb->data) must be in L1 cache. So basically the
prefetch(next_skb) is useless...
prefetch are not magic things. They have a cost (they increase the code size),
and should be used carefully.
Eric
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