[OLPC-devel] Network driver (?) and performance penalty

[Mitch Bradley]

Added to issue tracker as ticket #68,  http://dev.laptop.org/ticket/68 
<http://dev.laptop.org/ticket/68#preview>

Yoshiki Ohshima wrote:
>   Hello,
>
>   We, the member at the Viewpoints Research Institute, are working on
> the project to make Squeak environment work on OLPC.  (The "eToys
> team" in
> http://laptop.media.mit.edu/laptopnews.nsf/latest/news?opendocument=.
> is us.)
>
>   While taking some benchmarks, we noticed that having a USB-ethernet
> adaptor connected to a USB port (either through external hub or
> directly) makes things slow down, even with no data transmitted via
> network.  Most easily noticable is when our application is doing
> memory region copy (copy one concective memory region to another by a
> routine written in ANSI-C).  It is typically 20% slower than without
> network adaptor connected.  We tested it with Walter at OLPC office
> last week, and the mesh network shows similar effects.
>
>   One theory is that activity of the network driver is affecting the
> CPU cache or memory bus.
>
>   This is an interesting case because it may give us almost free 20%
> speed up.  Hopefully the gurus have time to take a look at it.  Even
> with 20% slowdown, Squeak looks pretty usable on OLPC.  We'll work on
> the Sugar integration of it in September.
>
>   Thank you!
>
> -- Yoshiki
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