In the case of zram, it reserves a portion of the physical RAM, and when the remaining physical RAM portion runs out, it begins compressing ram into the reserved portion. So the system slows down a bit as this compression starts happening. Nothing really adaptive about it to my knowledge but the result to the user is a noticeable slow down when there is high ram usage, which is a heads-up to me to close some stuff. Without it the system just locks up as soon as physical RAM is exhausted, without any warning, since it's fast up until that moment. Hope this makes sense. I'm not an expert on zram or other Linux RAM compression packages, so can't really answer questions about it beyond that.