🚀 go-pugleaf

I am posting this to the group because it might be of general interest /
provoke some discussion...

In article <9211082963@gandalf.moria>, u31b3hs@pool.informatik.rwth-aachen.de 
(Michael Haardt) writes:

>I would like to know some "throughput" values of the transputer-host
>link.
>
>When I use iserver, writing 1k blocks to the host gives me a performance
>of about 20k per second.  Using smaller blocks results in very reduced
>performance.

What are you doing with the data on the host side - are you throwing it away
or writing it to disk?  Are you using standard i/o libraries?  If so, whose
libraries?

>I wrote a small program to measure only transfer speed by reading data
>directly from the link.  The maximum throughput was about 110k per
>second.  I think the difference results in iserver being a single
                                                            ^^^^^^
>threaded server, so it can't receive new packets while it processes
 ^^^^^^^^
>packets, which reduces performance a lot.

This is only part of the story.  A multi-threaded server per se doesn't buy
you any performance improvement; your client i/o libraries and server
communication protocol have to be multi-threaded too.

I have written a multi-threaded version of the iserver and I have changed the
SP protocol to include a process identifier field in each packet.  A simple 
asynchronous mux/demux process sits between the standard Inmos libraries and 
the server; the mux/demux needs the process identifier to know to which process
to return reply packets.  This environment removes the synchronous i/o 
bottleneck that is a limitation of standard transputer servers; for example, 
one transputer process can be doing file i/o while another is blocked doing a
keyboard read.  Overall utilisation of the server is therefore improved.  Even
so, one would need to write one's own multi-threaded i/o libraries in order to 
reap any performance benefits at the individual file descriptor level.

Brendan
-- 
********************************************************************************
Brendan Murphy					brendan%buck.ac.uk@uknet.ac.uk
Department of Computer Science			Tel: 0280 814080
University of Buckingham, MK18 1EG, UK		Fax: 0280 822245
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