Re: Garbage Collection - The Trash Begins To Pile Up
Le Chaud Lapin wrote:
While looking for references, I found this statement about Java. Why
am I not suprised:
"Although Garbage Collection (GC) in Java attempts to simplify memory
management by relieving the developer from allocating, tracking and
freeing memory, it still cannot totally eliminate memory leaks. Objects
may be inadvertently kept beyond their useful lives, or may be
referenced so that GC will not scoop them up. Detecting memory leaks,
and finding and eliminating their root causes, are crucial steps in
improving the performance of a Java application."
http://websphere.sys-con.com/read/258406.htm
While not directly to the point but since you mentioned Java, most
(or some at least) of the Java garbage collectors exploit object
locality to reduce the number of objects that have to be GC'd. I.e.
objects are not allocated from GC'd memory unless they're referenced
outside of local scope. Local only objects are immediately dtor'd
as they leave scope.
This raises some interesting points. One is that pure GC is not as
efficient as some GC proponents would lead you to believe. The other
is that while you can use GC and get RAII like efficiency if the
GC implements it, you can't rely on it. So the ability to control
a major performance factor would be taken out of the hands of the
programmer.
And there are interesting situations like
for (;;) {
X x = new X();
...
}
A sufficiently smart compiler would recognise that the old
values of x can be collected right away. But do you want
programmers like that around? If they did that with something
with global scope, your application would spend most of it's
time in GC.
I suppose you could develop memory profiling tools that could
look for this kind of thing. There may be a trend here. We
develop smart tools so we can hire dumber programmers because
they're cheaper than good programmers.
--
Joe Seigh
When you get lemons, you make lemonade.
When you get hardware, you make software.
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