Re: Ethernet over Kernel Sockets

[Lukas Razik <linux@xxxxxxxxxx>]

Hello Mulyadi!


> > The preemption is off, because we have a Kerrighed (kerrighed.org)
> > patched kernel and I believe it doesn't work correctly with preemption
> > (at present) but I'll try that.
>
> Ahh...welcome to clustering brotherhood :)

Oh Thanks! :-)))
I still haven't tried to change the preemption model but I'll do that 
the next days because we had weekend and the short time I spent for my 
work I used to understand more about the callbacks in the linux kernel 
code...

I could replace the kernel thread for receiving UDP messages by an 
incomplete callback solution and now I have PingPong times of ~30µsec 
(over the native Ethernet interfaces I get ~23µsec) so that's an 
increase of only about 4µsec in one way instead of the 1msec (with the 
kernel thread solution)...
I think that I'm on the right way but there must be done more work. For 
example the checksum and (I believe) also the fragmentation stuff. So I 
think I must read much more kernel code and ask more people if they can 
help me...


> > How can I read the received data from the socket, what should I do after
> > reading, what must be locked and when...?
> > And what has to be done if I want send through a socket without the
> > sock_sendmsg() function which can't be called in interrupt context?
> >
> > Do you know any sources (books or something else) where I can read more
> > about socket callbacks? Because I've looked into the kernel sources
> > where these callbacks will be set but there are completely no comments...
>
> What if you better buy a copy of Understanding Linux Network stack? I
> hope that book can help you ....

That is a real good idea!
We have this book at our chair and unfortunately I could read nothing 
about the socket callbacks but there is much about the sk_buff struct 
and some about the checksum stuff.
Maybe that can help me with the further work...

Thanks again very much for your help and have a nice week!

Regards,
Lukas

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