Question

When I run a program (in linux) does it all get loaded into the physical memory? If so, is using shared libraries, instead of static libraries, help in terms of caching? In general, when should I use shared libraries and when should I use static libraries? My codes are either written in C or in C++ if that matters.

Answer 1

This article hits covers some decent ground on what you want. This article goes much deeper about the advantages of shared libraries

SO also has covered this topic in depth

Difference between static and shared libraries?

When to use dynamic vs. static libraries

Almost all the above mentioned articles are shared library biased. Wikipedia tries to rescue static libraries 🙂

From wiki,

There are several advantages to statically linking libraries with an
executable instead of dynamically linking them. The most significant
is that the application can be certain that all its libraries are
present and that they are the correct version. This avoids dependency
problems. Usually, static linking will result in a significant
performance improvement.

Static linking can also allow the application
to be contained in a single executable file, simplifying distribution
and installation.

With static linking, it is enough to include those
parts of the library that are directly and indirectly referenced by
the target executable (or target library).

With dynamic libraries, the
entire library is loaded, as it is not known in advance which
functions will be invoked by applications. Whether this advantage is
significant in practice depends on the structure of the library.