Contiguous physical memory from userspace

Question

Is there a way to allocate contiguous physical memory from userspace in linux? At least few guaranteed contiguous memory pages. One huge page isn\'t the answer.

Answer 1

Yes, if all you need is a few pages, this may indeed be possible.

The file /proc/[pid]/pagemap now allows programs to inspect the mapping of their virtual memory to physical memory.

While you cannot explicitly modify the mapping, you can just allocate a virtual page, lock it into memory via a call to mlock, record its physical address via a lookup into /proc/self/pagemap, and repeat until you just happen to get enough blocks touching eachother to create a large enough contiguous block. Then unlock and free your excess blocks.

It's hackish, clunky and potentially slow, but it's worth a try. On the other hand, there's a decently large chance that this isn't actually what you really need.