Re: [9fans] running plan9 : an ideal setup?

[erik quanstrom <quanstro@quanstro.net>]

> I think it is very realistic.  They modified standard bsd
> stack (I don't know its present state but back when I worked
> on it, it needed to be simplified quite a bit).

i think a no lock tcp stack from 1990 hacked to be even less sophisticated is anything
but realistic.  it's pure fantasy that one can avoid proper locking today.

and at 10gbe packet rates even 400 instructions per packet (* 1.5 for the reply)
is not a trivial expense.

> I haven't looked into why on the RPi plan9's tcp performance
> is about 30-40% of that on linux (which works near wire speed).
> For the local case it doesn't matter much in any case.

(a) allocb() relies on deathly slow malloc; cf. qallocb in 9atom, which upps performance quite a bit
(b) usb is not as fast,
(c) send and recieve in plan 9's tcp are not as decoupled as they could be,
this leads to latency in sending after the window opens, or latency in opening
the window.

- erik