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I’m curious about the supposed memory advantages of dynamic linking: on average how many different executables share each page of memory? What about when memory

I’m curious about the supposed memory advantages of dynamic linking: on average how many different executables share each page of memory? What about when memory is in high demand? How high does that average become? What is the probability that a page of a shared library is already in memory (cache or otherwise) when it needs to be loaded, and in particular the probability that it is there because another program loaded it). My guess is that apart from eg libc, the average is pretty low (ie 1 for the pages that aren’t free).

saagarjha 6y ago
I think this depends heavily on your platform and how often libraries are reused. On macOS, for example, most libraries aside from libc are loaded R/O or CoW quite literally hundreds of times, because every app shares AppKit and WebKit and Security and the dozens of other platform frameworks (and their private dependencies!) that are basically "free" to use and ship with the system and so have very high adoption. On more "coherent" Linux distributions I'm sure things like GTK, glib, OpenSSL, zlib are used by a lot of things too. Sure, there's going to be a lot of one-off dynamic libraries too, but there's a lot of duplication with the popular dependencies and then a long tail.