But 4 KiB pages aren't the only size that most CPU and OS architectures support. There's usually also something called large or huge pages, because having to manage only a fixed small size like 4 KiB isn't efficient in certain cases.
I remember those stuff sometimes mentioned on discussion about docker and virtual machine. But AFAIK it's not enabled by default on some OS and linux distro. Although when it's enabled on Linux, some application can take advantage of it without additional programming.
Transparent huge pages are more or less completely handled by the Linux kernel. Depending on your current kernel configuration (see the
next section) it can happen that memory in your application is allocated in huge pages without you - as the programmer - even knowing. It may even happen that memory for your application that was not originally allocated in a huge page is later transformed into a huge page!