netdev - Re: skbuff truesize incorrect.

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Message-ID: <537E5C4D.4040209@mentor.com>
Date:	Thu, 22 May 2014 21:21:33 +0100
From:	Jim Baxter <jim_baxter@...tor.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Vlad Yasevich <vyasevich@...il.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>, <kamal@...onical.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	<edumazet@...gle.com>, <mszeredi@...e.cz>, <fw@...len.de>
Subject: Re: skbuff truesize incorrect.

On 22/05/14 20:59, Eric Dumazet wrote:
> On Thu, 2014-05-22 at 20:39 +0100, Jim Baxter wrote:
> 
>> I now think that the correct solution here is to create a new smaller
>> skb and copy the data from the sub packets into it.
> 
> For low speed devices, this is indeed the best way.
> 
> (this is called copybreak in some nic drivers)
> 
> 
> 
Thank you Eric.

It is USB device that can handle 480Mbits/s so a middle speed device.

It looks like it is the normal trade off of speed versus memory. Either
I can use skb_clone for speed but that will impact memory with multiple
skb's of 16k or I copy the data to keep the memory usage low. Though
copying 2k of data into an skb will not likely be a massive overhead.

Jim
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