[vidarh]

Fragmentation issues depends greatly on language. E.g I'm (perpetually, it seems) working on a Ruby compiler, and I slotted in a naive gc as a starting point and instrumented it.

Turned out the vast majority of allocations are tiny object instances of a handful of different sizes. As a result minimizing fragmentation is as easy as allocating pools of a fixed size for small objects, and round up larger objects to a multiple of block size. There are still truly pathological patterns possible, and a compacting / generational gc may still be worth it later both to deal with that and to reduce the cost of a collection, but for a lot of uses you can get away with simple options like that.