Read the quick comparison here:
Linux Memory Management API Quick Primer [Download PDF]
Gautam Bhanage | www.Bhanage.com | Pub2: GDB2019-001 June 2019
At a high level:
1. kmalloc for all generic memory allocation
2. kmem_cache_alloc for repeatetive structs that need allocations. These structures typically need to be accessed frequently (and are L1 & L2 cache aligned by the kernel).This is done much more efficiently through the slab allocator.
3. vmalloc() - allocates virtually contiguous memory. Not really useful from a linux kernel driver perspective.
