Thu, 01 Jan 2004 21:09:25 +0000
I lied. Well, I was mistaken: in the course of tidying up purify so that I might understand it, I managed to break it. !(a && !b) is not, De Morgan will happily tell you, the same thing as (!a && b). Doh. I was copying a whole bunch of stuff (constant boxed vectors, or possibly unboxed inconstant vectors) to static space that should have been happy in read-only space. So static space was up to 9.5Mb from its normal 5, hence the extra time spent checking it. If it takes an approximate extra 10s to GC when there's an extra 5Mb of static space to check, this also goes some way to explain why CMUCL is faster: in 18e it only has 2.5Mb of static space, so that's 5s off the GC time, leading us to predict that it should take about 15s. It's actually a bit under (13s) but that's only a couple of seconds still to claw back, then.
All times are to execute (time (dotimes (i 400) (gc)))