Re: [9fans] netpipe results

[presotto@plan9.bell-labs.com]

Looks good.  Is the 'data size' the size of a single write i.e. what the
NetPIPE paper calls 'block size'?  If the latter, I can guess at some
explanations to start working at improving things.

Looks like things start to fall off around 32K byte writes.  Just looking
at numerology, that's what Maxatomic is set to in port/qio.c.  It's
the point we start breaking writes into multiple blocks.  I assume that
will have some affect though not a huge one.  The drop we see at that
point is more than I would expect.  The real nose dive happens
twixt 64k and 100k.  64k is the size of the per channel output queue.
After that, the system has to wait for the queue to half empty before
queuing any more.  Just for a wild guess, it looks like we're getting
screwed by interaction twixt that histeresis and the process getting
rescheduled.  There's similar problems with the size of the input
per channel queue (64k).  Perhaps we should have spent more time
reading Kleinrock.

These are just wild guesses.  I'll start playing to see if I can explain
it, and preferably make it go away.  I welcome anyone else doing the
same.

Thanks much.  It'll make a fun distraction.