[racket] disable garbage collection

>> Good points.  For my list of reasons, I was thinking only of disabling GC for the lifetime of a process, but there are additional reasons that one might want to temporarily inhibit GC for a shorter duration.
>
> An even simpler thing to do, which won't give you hard-real-time guarantees but will work most of the time, is to allow the programmer to say "Please garbage-collect NOW" just BEFORE a time-critical section of code.  I could have sworn there used to be a (gc) function that did this, but it doesn't seem to work in 5.1.

Are you referring to collect-garbage?

http://docs.racket-lang.org/reference/garbagecollection.html?q=collect#%28def._%28%28quote._~23~25kernel%29._collect-garbage%29%29