Selector Uniquing in the dyld Shared Cache
Snow Leopard’s dyld shared cache uniques Objective-C selectors, and Snow Leopard’s Objective-C runtime recognizes when the selectors in a shared library are already uniqued courtesy of the shared cache. About half of the runtime’s initialization time is eliminated, making warm app launch several tenths of a second faster. Typical memory savings is 200-500 KB per process, adding up to a few megabytes system-wide. When this optimization ships on the iPhone OS side, it’s estimated to save 1 MB on a 128 MB device. The iPhone performance team would pay any number of arms and legs for that kind of gain.
