Maurizio, you haven't really said what you want to use AOLserver
for. What is your use case? Evalauating the technical
merits of different esoteric approaches isn't very useful without
that.
I think (could be wrong though) that whether a memory allocator is
subject to fragmentation problems or not has little or nothing to do
with whether or not the system uses garbage collection. It also
doesn't necessarily have much to do with whether the applications
memory use continues to grow over time either. Remember that the
operating system malloc does not necessarily release
memory from the process just because you call free to release it!
(And that varies across platforms.) That's one of the things Zoran
and the other Naviserver guys wrestled with in their VTMalloc work, I
believe.
Also, I suspect that retrofitting a Boehm-Demers-Weiser conservative
garbage collector to Tcl and AOLserver, while certainly doable, is
unlikely to achieve your goals. "Conservative" garbage collectors are
just that, conservative - they lack full knowledge of the
application's memory use, and when unsure, leave memory uncollected.
Thus, all conservative collectors leak to some degree over time.
Whether or not that's a problem is a matter of use case and of degree,
but it's why conservative collectors are reputed do be
unsuitable for genuinely long running, high use, high reliability
servers.
AFAIK, dropping a Boehm-Demers-Weiser garbage collector into existing
C code is primarily a way to avoid having to fix your malloc/free bugs
and/or to have code written in a garbage collected language interact
well with C code, not a way to get perfectly leak free code. (Garbage
collection is a truly wonderful feature, but it's no magic wand...) I
suppose both using a conservative collector and carefully
calling free() might work better than either alone - dunno, I have no
practical experience there.
For a super reliable leak free long-running server, you want either an
exact garbage collector (which requires language support, and thus is
more complicated and cannot simply be dropped into existing C
code), or you want what AOLserver already has - mannual malloc and
free. And then track down the few remaining tricky leaks you've
missed...
