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Re: [patch 05/13] remove last_rx update from loopback device

To: akpm@xxxxxxxx
Subject: Re: [patch 05/13] remove last_rx update from loopback device
From: Jeff Garzik <jgarzik@xxxxxxxxx>
Date: Tue, 15 Mar 2005 17:41:39 -0500
Cc: davem@xxxxxxxxxxxxx, netdev@xxxxxxxxxxx, christoph@xxxxxxxxxx, nirajk@xxxxxxxxxxxxxx, christoph@xxxxxxxxxxx, Shai@xxxxxxxxxxxx
In-reply-to: <200503152222.j2FMMbhG016805@shell0.pdx.osdl.net>
References: <200503152222.j2FMMbhG016805@shell0.pdx.osdl.net>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040922
akpm@xxxxxxxx wrote:
From: Christoph Lameter <christoph@xxxxxxxxxx>

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 <nirajk@xxxxxxxxxxxxxx>
Signed-off-by: Christoph Lameter <christoph@xxxxxxxxxxx>
Signed-off-by: Shai Fultheim <Shai@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---

 25-akpm/drivers/net/loopback.c |    2 --
 1 files changed, 2 deletions(-)

diff -puN drivers/net/loopback.c~remove-last_rx-update-from-loopback-device drivers/net/loopback.c
--- 25/drivers/net/loopback.c~remove-last_rx-update-from-loopback-device Tue Mar 15 14:19:53 2005
+++ 25-akpm/drivers/net/loopback.c Tue Mar 15 14:19:53 2005
@@ -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;

I disagree. loopback.c is doing precisely what it should be doing.

        Jeff




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