Slows up garbage collection during the execution of code that allocates a lot of space.
with-heavy-allocation &rest body => result
The forms for which you want the garbage collector to behave differently from normal.
The result of executing body.
with-heavy-allocation is for use with code that allocates a lot of space but is not interactive. It ensures that garbage collection (GC) is carried out less frequently while these forms are being executed. However, each GC may take longer.
In LispWorks 5.0
with-heavy-allocation is implemented only in 32-bit LispWorks. In version 5.1 and later it is implemented in 64-bit LispWorks as well.
LispWorks User Guide and Reference Manual - 20 Sep 2017