Faster way to move memory page than mremap()?

Question

I\'ve been experimenting with mremap(). I\'d like to be able to move virtual memory pages around at high speeds. At least higher speeds than copying them. I have some ideas for

Answer 1

What makes you think mremap could ever be efficient for swapping single 4k pages? At the very least, a round-trip to kernelspace even just to read a single value (like pid) and return it will cost more than moving 4k of data. And that's before we get to the cache invalidation/TLB costs of remapping memory, which I don't understand well enough to address in this answer, but which should have some serious cost.

mremap is useful for basically one thing: implementing realloc for large allocations that were serviced by mmap. And by large, I mean probably at least 100k.