netdev - Re: Generic rx-recycling and emergency skb pool

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Message-ID: <1278142260.2474.76.camel@edumazet-laptop>
Date:	Sat, 03 Jul 2010 09:31:00 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	sebastian@...akpoint.cc, netdev@...r.kernel.org, tglx@...utronix.de
Subject: Re: Generic rx-recycling and emergency skb pool

Le vendredi 02 juillet 2010 à 23:46 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Sat, 03 Jul 2010 08:23:25 +0200
> 
> > Maybe its time to provide new API, so that a driver can build an skb at
> > the time RX interrupt is handled, not at the time the rx ring buffer is
> > renewed. RX ring should only provide the data part to NIC, and skb
> > should be built when NIC delivers the frame, so that we provide to IP
> > stack a real hot skb.
> 
> Drivers do this already, and in fact I am very sure I'm mentioned this
> to you at least other time in the past, and one such driver is NIU :-)

You did indeed. I should said "provide a generic and universal API",
usable by average NIC driver, not only big ones. (NIU is more than
10.000 lines of code ;) )

NIU still uses netdev_alloc_skb() API. I was thinking of a function to
allocate and populate the sk_buff, but data part provided by caller.

> 
> It's trivial to do with devices which work on power-of-2 chopped up
> pages.  In fact I'm surprised that RX buffer management scheme is
> not more prevalent in network devices.

Many of them were written in last century :)



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