General Problems for GC'ed Applications?

[Walter Bright]

Karen Lanrap wrote:
> I disagree. Assume a non GC'ed program that allocates 1.5 GB to 1.7 
> GB memory, from which 0.7 GB to 0.9 GB are vital data. If you run 
> this program on a machine equipped with 1 GB, the OS will swap out 
> the 0.8 GB data that is accessed infrequently. Therefore this 
> program cause swapping only if it accesses data from the swapped 
> out part of data and the size of the swapped data will be 
> approximately bounded by doubling the size of the data needed to be 
> swapped back.
> 
> This changes dramatically if you GC it, because on every allocation 
> the available main memory is exhausted and the GC requires the OS 
> to swap all 0.8 GB back, doesn't it. 

No, it doesn't require it to all be swapped in. It fact, it doesn't 
require any of it to be swapped in, unless a full collect is done. Full 
collects are not performed on every allocation - that would be a 
terrible design if it did.