OK6410A Development Board (VIII) 38 linux-5.11 OK6410A Why do we need so many memory managers?

Can't I just use memblock in the end?

Is it not possible to skip memblock and directly set buddy?

The difference between memblock and buddy

Why is buddy the basis of memory manager and other managers?

Why do we need to create slab and vmalloc after creating buddy?

What are the characteristics of these memory managers???

The third stage consumer

The third stage is to establish a buddy

Alloc_pages requests are continuous pages of physical memory.

Physical addresses are continuous, virtual addresses must be continuous

But at least one page or more

question:

1. The minimum memory size that can be requested by the buddy API is one page, and it cannot be smaller

2.alloc_pages If you apply for 2 or more pages, it will return correctly only when there are 2 consecutive pages in physical memory; otherwise, it returns 0

The fourth stage consumer

Used to solve buddy's first problem

solution:

Think of buddy as a big memory wholesale agent (buddy memory allocator) and build a small agent (slab memory allocator)

slba buys memory from buddy, divides the memory into smaller blocks (A) (less than 1 page), and manages them.

Users wholesale A from slab

other:

Because the second problem is not solved, as long as the application is successful (no matter how big it is), it will definitely be the following status:

Physical addresses are continuous, virtual addresses are continuous

The fifth stage consumer

Used to solve buddy's second problem

solution:

Instead of building a distributor based on buddy

Instead, it encapsulates a layer

This extra layer mainly uses the page table to map discontinuous physical memory into the virtual kernel address space to make it appear continuous.