netdev - Re: [PATCH V6 2/4 net-next] skbuff: Add userspace zero-copy buffers in skb

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Message-ID: <1306444117.5180.62.camel@localhost.localdomain>
Date:	Thu, 26 May 2011 14:08:37 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, mst@...hat.com,
	Avi Kivity <avi@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 2/4 net-next] skbuff: Add userspace zero-copy
 buffers in skb

On Thu, 2011-05-26 at 22:55 +0200, Eric Dumazet wrote:
> Le jeudi 26 mai 2011 à 13:24 -0700, Shirley Ma a écrit :
> 
> > I could reduce callback pointer by moving it to *arg, but not desc,
> this
> > indicates that which buffer DMA hasn't done yet in *arg.
> 
> 
> I guess you dont need to use skb itself to hold all your states ?
> 
> I understand its convenient for you, but I believe its worth the pain
> to
> use only one pointer to a (small) object where you put all your stuff.
> 
> Some machines alloc/free millions of skbs per second. 
> 
> If/when most skb uses are for userspace zero-copy buffers we can
> embbed
> your small object in skb itself ;)

You are right, w/o this desc, there will be lots of alloc/dealloc in the
caller side. To have better performance, maybe I should have changed
most skbs to use zero-copy buffers. :)

Ok, for now let me try to move it to caller, just leave one pointer
*uarg here.

Thanks
Shirley

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