Re: Unix domain sockets being slooooooooooooooooooooooooowwwwwwwww
Rogier Wolff (R.E.Wolff@BitWizard.nl)
Thu, 30 Oct 1997 16:24:51 +0100 (MET)
Richard B. Johnson wrote:
>
> On Thu, 30 Oct 1997, Alan Cox wrote:
>
> > > 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.
>
Dick,
Alan was careful not to tell anybody that you were wrong, but he
just pointed out that "data bandwidth" is not the only overhead
to take into account and that this overhead can be significant.
Roger.
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