Re: [parisc-linux] C110 builtin nic slow?

[Grant Grundler <grundler@parisc-linux.org>]

On Mon, Nov 10, 2003 at 03:00:37PM +0100, Joel Soete wrote:
>                         if (pkt_len > rx_copybreak) {
>                                 struct sk_buff *newskb;

yup - the rx_copybreak support is exactly what I'm talking about.
tulip driver has similar support.

> /* Copy frames shorter than rx_copybreak, otherwise pass on up in
>  * a full sized sk_buff.  Value of 100 stolen from tulip.c (!alpha).
>  */
> static int rx_copybreak = 100;

The comment is wrong. Tulip uses 1518 for nearly everything but x86.
ie it copies all packets since the MTU is <= 1518.


> This last notice seems what I am loocking for?
> Have you a better idea then try and test (ie rx_copybreak=512, test, rx_copybreak=256,
> ... and btw rx_copybreak = PKT_BUF_SZ == 1536)?
> Or is it better to tiddle code before?

I don't know. It depends on if/when the misaligned access happens.
It's possible the misaligned access is less expensive than
the full copy on your machine.

grant