On 1/13/2014 12:57 PM, Brad Roberts wrote:
The key advantage that moving gives to a GC is to allow it to have a block of
memory that it can do allocations out of by simply bumping the pointer. When
that region is full, a minor collection kicks in, moving anything still alive
out to a different block of memory, then reset the region for re-use. Pinned
objects == region can't be emptied for reuse. That leads to fragmentation and
free list maintenance and you're right back with a more typical allocator.
Not to say there aren't other ways of doing things, but with random objects
becoming pinnable puts a big damper on things unless you can identify all the
objects that might be pinned and isolate them. But I doubt that's really
knowable up front.
The reason pinning doesn't particularly impede this is because pinning is rare.
