Performance issue with GC

[Yuxuan Shui via Digitalmars-d-learn]

I have a little data processing program which makes heavy use of 
associative arrays, and GC almost doubles the runtime of it (~2m 
with GC disabled -> ~4m).

I just want to ask what's the best practice in this situation? Do 
I just use GC.disable and manually run GC.collect periodically?