Let's look at the following diagram, showing us the different memory allocators that exist on a Linux-based system, and discuss it later. (inspired by http://free-electrons.com/doc/training/linux-kernel/linux-kernel-slides.pdf):
Overview of kernel memory allocator
There is an allocation mechanism to satisfy any kind of memory request. Depending on what you need memory for, you can choose the one closest to your goal. The main allocator is the Page Allocator, which only works with pages (a page being the smallest memory unit it can deliver). Then comes the SLAB Allocator which is built on top of the page allocator, getting pages from it and returning smaller memory entities (by mean of slabs and caches). This is the allocator on which the kmalloc Allocator relies.
