Any advice for GC/memory debugging

[Alan Knowles]

Having fleshed out an SMTP server, I've now started testing it against a 
good load level.

Apart from the various thread issues in phobos (getHostbyName is not 
thread safe etc./ using udns solved alot of this...) - my bigger worry 
is memory management.

With GC enabled/or even disabled, the memory pool will rise to ~ 200Mb 
from the baseline of ~20K and run out of memory on the box it's running 
on. The test box we have peaks at about 30 concurrent 
connections/threads. - compiled using GDC (as it's FreeBSD)

 From what i've seen, there is no real way to disable the Garbage 
collection, in terms of stopping it from managing the 
allocation/deallocation of memory? as it is too intertwined in the 
management of things like char[] etc..

Has anyone found good ways to  analyze where the application may be 
leaking memory/allocating to much memory - hooks in the in/out 
properties of methods ?

Is there any way to compact the memory, as the pool appears to jump 
quite dramatically from ~ 64k->100Mb->250Mb, even though it looks like 
the used pool is significantly smaller..

I'm basically fishing for ideas here, as I've got a whole day tomorrow 
to start sticking in debugging code to find some answers...

Regards
Alan