copy-on-write

Letting two programs share the same pages until one of them writes; only then does that page get its own private copy.

Copy-on-write maps shared frames read-only in both address spaces (after fork, or for private file mappings); a write faults, and the handler copies the frame, maps the copy writable and retries the store.

Examples

After fork, parent and child share every page until one of them writes; only that page is then copied.