Hunting down rogue memory allocations?

[Gary Willoughby via Digitalmars-d-learn]

Say i have created a program written in D, what tools are 
available for me to track memory allocations?

If you write a program and its performance is slow because you 
suspect too many allocations are taking place in unrecognised 
areas, what tools or techniques do you use to find where they are 
and eliminate them?