> > I think there's a minimum packet length over ethernet that is killing you
> > with overhead. I think it's 64 bytes. If you have a 1-byte semaphore, you
> > are only using about 1/64th of the available data bandwidth.
>
> The actual wasted 63 bytes is but a tiny fraction of the cost of getting
> a packet to wire - a lot of it is going to the hardware setup overheads,
> and even the linux syscall overhead too
>
> Effectively its an equation of the form
>
> large_overhead+(small_cost*bytes)
> ---------------------------------
> bytes
>
> which means small messages get you into poor performance areas. Doing it
> with tcp not udp really makes it fun
>
Alan,
I was careful to use the words "data bandwidth", i.e., the bandwidth
available for useful stuff. This takes all the (enormous) built-in
overhead and normalizes it out of the way.
Cheers,
Dick Johnson
Richard B. Johnson
Project Engineer
Analogic Corporation
Penguin : Linux version 2.1.60 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.