# Re: \[PATCH V7 2/4 net-next\] skbuff: Add userspace zero-copy buffers in skb

- From: David Miller \<davem@davemloft.net\>
- Date: 2011-06-28 23:35:21 
- List: netdev
- Page: https://ratatoskr.run/netdev/2011/06/3735201
- Thread: https://ratatoskr.run/netdev/2011/05/3721758/t.md

```text
From: Shirley Ma <redacted>
Date: Tue, 28 Jun 2011 09:51:32 -0700

> On Mon, 2011-06-27 at 15:54 -0700, David Miller wrote:
>> From: Shirley Ma <redacted>
>> Date: Mon, 27 Jun 2011 08:45:10 -0700
>> 
>> > To support skb zero-copy, a pointer is needed to add to skb share
>> info.
>> > Do you agree with this approach? If not, do you have any other
>> > suggestions?
>> 
>> I really can't form an opinion unless I am shown the complete
>> implementation, what this give us in return, what the impact is, etc. 
 ..
> You can see the overall CPU saved 50% w/i zero-copy.
> 
> The impact is every skb allocation consumed one more pointer in skb
> share info, and a pointer check in skb release when last reference is
> gone.
> 
> For skb clone, skb expand private head and skb copy, it still keeps copy
> the buffers to kernel, so we can avoid user application, like tcpdump to
> hold the user-space buffers too long.

Ok, now show me the "complete implementation".  I'm as interested in
the code as I am in the numbers, that's why I asked for both.
```