[E-Lang] FW: Reasearch ideas in HDC
Mon, 29 Jan 2001 08:49:01 -0500
Karp, Alan wrote:
> > > IBM researchers, he said, are now trying to perfect software that
> will identify
> > > and repair the underlying coding errors that cause software aging.
> The last paragraph is quite disturbing. How many security holes do you
> think they'll introduce? The good news is that they probably won't be
> fixing any E programs.
I assume they mean tools that bring problems to the attention of
programers and then help fix the problems, not robots that automatically
rewrite running machine code.
>>> "Aging" software
>>> Lockups occur as often as weekly or monthly, Bradicich said, because
>>> sound software accumulates coding abnormalities that build up and drain
>>> in a process called "aging." If a computer isn't restarted to clear the
>>> erroneous instructions, the microprocessor eventually won't know
>>> what to do
>>> next, and it freezes.
It looks to me that what they are trying to fix here are resource
leaks. As time goes on processes allocate memory but never free it,
either because they incorrectly no longer have a reference to it (C) or
because they do (java). The same thing happens on the scale of
processes; a process is started and hangs, waiting perhaps for some
deadlock to resolve, eventually a new request starts a new process for
the same task but the old one doesn't get killed.
How do E and EROS handle resource leaks? Persistence can make the
problem much worse. In the quote it is implied that they treat the
problem by rebooting the computer, which frees all (most) resources. If
I understand correctly, in EROS this approach will not work at all,
rebooting leaves the system in exactly the state it was in before.
How does E do manage memory? Does it rely on Java's garbage collection?
If so, there is a problem because Java can leak memory quite badly (one
reference to a high level object makes everything live forever).
What do you do when a system like EROS gets totally clogged by leaked
resources? Don't say we will keep that from ever happening - it WILL