linux-kernel - Re: [PATCH 2.6.34-rc6] net: Improve ks8851 snl transmit performance

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Message-Id: <20100516.002607.84408834.davem@davemloft.net>
Date:	Sun, 16 May 2010 00:26:07 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	Tristram.Ha@...rel.Com
Cc:	ben@...tec.co.uk, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, x0066660@...com, s-jan@...com
Subject: Re: [PATCH 2.6.34-rc6] net: Improve ks8851 snl transmit performance

From: "Ha, Tristram" <Tristram.Ha@...rel.Com>
Date: Thu, 6 May 2010 15:50:27 -0700

> From: Tristram Ha <Tristram.Ha@...rel.com>
> 
> Under heavy transmission the driver will put 4 1514-byte packets in
> queue and stop the device transmit queue.  Only the last packet
> triggers the transmit done interrupt and wakes up the device
> transmit queue.  That means a bit of time is wasted when the CPU
> cannot send any more packet.
> 
> The new implementation triggers the transmit interrupt when the
> transmit buffer left is less than 3 packets.  The maximum transmit
> buffer size is 6144 bytes.  This allows the device transmit queue to
> be restarted sooner so that CPU can send more packets.
> 
> For TCP receiving it also has the benefit of not triggering any transmit interrupt at all.
> 
> There is a driver option no_tx_opt so that the driver can revert to
> original implementation.  This allows user to verify if the transmit
> performance actually improves.
> 
> Signed-off-by: Tristram Ha <Tristram.Ha@...rel.com>

First, if you want to post patches you have to format them properly as
ascii text with no longer than 80 column lines in your commit message.
I really don't want to hear about your email client being a reason
you can't do this properly :-)

Second, I don't think you can use the skb->ip_summed for this hacked
state tracking you are using.  The packet might be shared with other
entities, and therefore if you change the field it won't be correct
for them any more.
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