Mike Meyer wrote:
> While Heisenberg's uncertainty doesn't apply as described to macro
> events, the concept certainly works. If you instrument a kernel to
> find performance problems, you've just slowed the kernel down, and
> changed what routines get used when. And I'm sure we've all had the
> experience of adding a print to try and catch a bug, and the bug
> vanishes.

This only happens if you don't know what you are doing.
It's very easy to do instrumentation which subtracts
itself out of the overall count, if the instrumentation
is for profiling. For debugging of timing sensitive
problems, you have to use non-invasive techniques in
order to avoid changing the timing. It isn't rocket
science.

As to the idea that the observer always changes the thing
being observed, that's silly. It's only true if the
observer isn't copetent, until you get down to the quantum
level.

> Given that computers are so blasted cheap these days, and the
> availability of open source software, there's a lot of learning that
> can be done without stealing cycles from someone else.

Actually, the use of individual equipment is one of the
things that's wrong with todays CS classes. If you do
your work on your own machine at home, rather than using
shared resources, you never learn to "play nice" with
other software on the system that you didn't plan on.
It's one of the reasons Windows Systems are so fragile
these days, when programs from different vendors are loaded
on them: the programmers responsible never had to learn
to "play nice with the other kids".

> No, they'll just slow them donw, possibly screw up the accounting, and
> similar things that can make peoples lifes miserably. Read the book by
> the guy at LBL who helped track down a couple of crackers, even though
> they mostly used a "look but don't touch" methodology on his
> computers. His web site seems to be gone, or I'd send over there to
> order a Kleine bottle from him as well.

You mean Clifford Stoll's "The Cuckoo's Egg: Tracking a Spy
Through the Maze of Computer Espionage", in which he used
non-invasive observational teqniques that did not impact
what he was observing? 8-).

I think his neo-luddite books "Silicon Snake Oil: Second
Thoughts on The Information Highway" and "High Tech Heretic:
Why Computers Don't Belong in the Classroom and Other
Reflections by a Computer Contrarion" are a lot more telling,
don't you?

        "Ultimately, though, Stoll contradicts himself too
         often: in one sentence, he fears the demise of
         libraries; in the next, he states why book-based
         libraries won't disappear. What's more, he
         undermines his argument's seriousness with comic
         footnotes and deliberately improper grammar. Still,
         his book signals the first wave in the backlash
        against the race to the future that computer
         technology now represents." -- Benjamin Segedin

PS: The people he was writing about in "The Cuckoo's Egg"
we definitely not just observers...

-- Terry

To Unsubscribe: send mail to majordomoFreeBSD.org
with "unsubscribe freebsd-security" in the body of the message

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]