Re: Un aligned addresses

[Willy Tarreau <willy@w.ods.org>]

On Thu, Dec 22, 2005 at 12:06:46PM +0530, Conio sandiago wrote:
> Hi all
> i have a embedded monta vista linux running.
> i have developed a ethernet driver.
> Its working Ok,
> But i am facing some problem with the throughput.
> 
> After a lot of observation ,
> i observed that i am getting un-aligned addresses of the data payload
> from the TCP/IP stack.because of this problem i always have to do
> memcpy to a word aligned buffer,because of which throughput is reduced
> significantly.
>
> Does anybody has some solution for this.

I guess your driver is not working that much OK yet. Many (most)
ethernet boards today will align the IP header on a 4 or 16 bytes boundary.
By default, the ethernet header being 14 bytes, it unaligns the IP header.
But some boards will leave a hole between those. Probably that your driver
needs to tell the hardware to do this. Or maybe you can program the DMA
to get on 4x+2 so that IP gets aligned ?

Anyway, I don't know whether I'm loosing my time because last time
you sent such a report about your driver, I asked for a little more
precisions, which I never received.

> Regards
> conio

Willy

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