On Tue, Aug 30, 2011 at 12:04 AM, Helmut Eller <heller@common-lisp.net>wrote:
* Raymond Toy [2011-08-29 21:26] writes:
(We should also have a mark&compact GC for the oldest generation, but that's another issue.)
Is there something wrong with the current Cheney copying collector that is used for the oldest generation? (I think that is what is used for the oldest generation.)
If we have a lot of stable memory, say 1GB in the oldest generation, then we need another 1GB for to-space to run the copying GC. A compacting GC tries to move all live objects in the 1GB area to "one side", freeing up the holes left behind by dead objects. That needs much less extra memory, I guess a few MB. It may be a bit slower, though.
An interesting idea. Full GCs don't happen that often, I think, so the slowdown, if any, may not be noticeable. From some comments from Luke Gorrie quite a long time ago, the main time spent in GC was actually in GCing the static space. At least for his test cases.
Ray