2005-03-07 22:53:26

by Christoph Lameter

[permalink] [raw]
Subject: [PATCH] remove last_rx update from loopback device

The last_rx field in the loopback driver is updated on every xmit but
is not used otherwise. Accesses to ->last_rx cause unecessary traffic on the
interlink for NUMA systems which limits the performance of the loopback device.

The comment given at include/linux/netdevice.h says that last_rx may be
used for future network-power-down code, which is likely not relevant
for the loopback device (please let me know if it is otherwise ..).

Signed-off-by: Niraj Kumar <[email protected]>
Signed-off-by: Christoph Lameter <[email protected]>
Signed-off-by: Shai Fultheim <[email protected]>

--- linux-2.6.9.clean/drivers/net/loopback.c 2005-02-28 21:54:20.000000000 -0800
+++ linux-2.6.9.clean-loop/drivers/net/loopback.c 2005-03-03 22:59:34.068607608 -0800
@@ -144,8 +144,6 @@ static int loopback_xmit(struct sk_buff
return 0;
}

- dev->last_rx = jiffies;
-
lb_stats = &per_cpu(loopback_stats, get_cpu());
lb_stats->rx_bytes += skb->len;
lb_stats->tx_bytes += skb->len;