On linux you can use remap_file_pages[1] to setup your magic ring buffer. Yes, these days it is emulated in the kernel, but here we only care about setting up t

On linux you can use remap_file_pages[1] to setup your magic ring buffer. Yes, these days it is emulated in the kernel, but here we only care about setting up the expected duplicated mapping of anon pages instead of minimizing the allocations of VMAs. Also linux has MADV_DONTFORK, would that allay your concerns? (there is a potential race between mmap and the madvice call, but if you are forking in a multithreaded program you have worse concerns). [1] https://man7.org/linux/man-pages/man2/remap_file_pages.2.html https://man7.org/linux/man-pages/man2/remap_file_pages.2.htm...