why GC not work?

[mzfhhhh via Digitalmars-d-learn]

On Saturday, 7 February 2015 at 06:08:39 UTC, ketmar wrote:
> On Sat, 07 Feb 2015 04:30:07 +0000, Safety0ff wrote:
>
>> False pointers, current GC is not precise.
>
> not only that. constantly allocating big chunks of memory will 
> inevitably
> lead to OOM due to current GC design. you can check it with 
> manual
> freeing. there were some topics about it, and the solution is 
> either use
> 64 bit OS ('cause the memory is here, but there is no address 
> space to
> allocate it), or use `malloc()` and `free()` from libc.

hi,i still have two questions:

1. how large is the "big chunks"  ? 10MB? 50MB? ...
       where are topics about this？
       if I don't know the exact size, it is very likely a memory
leak

2. "auto buf = new byte[](1024*1024*100);"
       now the gc can't free this buf.
       can i free it by manual?