[Linux Kernel Memory Management] Partner Allocator ② (Partner Allocator Allocating Memory Process)

1. The memory allocation process of the partner allocator

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The partner allocator allocates/ releases physical pages in units of "orders" ;

Order (Order): the unit of the number of physical pages, $n$ -order page blockrefers to$2^n$ consecutive"physical pages";

Page/order concept reference [Linux Kernel Memory Management] Partner Allocator ① (Partner Allocator Introduction | Page Block, Order | Partner) Blog;

"Buddy allocator" allocates memory process: suppose to allocate $n$ -order page blocks;

1. Query n-order page blocks

Query whether there is currently free $n$ -order page blocks,

• If there is, assign it directly ,
• If not, go to the next step, query $n+1st$ order page block;

2. Query n + 1 order page blocks

Query whether there is currently free $n+1st$ order page block,

• If there is, put $n+Tier\; 1$ Page Blocks Divided into$2$ nn_$n$ -order page blocks,

  • one piece insert free $n$ -order page block linked list;
  • A block is allocated directly ,

• If not, go to the next step, query $n+2nd$ order page block;

3. Query n + 2-order page blocks

Query whether there are currently free $n+2nd$ order page block,

• If there is, put $n+Level\; 2$ Page Blocks Divided into$2$ n$n+1st$ order page block,

  • Block Insert Freen $n+1st$ -order page block list;
  • A block will be $n+Tier\; 1$ Page Blocks Divided into$2$ nn_$n$ -order page blocks,
    • one piece insert free $n$ -order page block linked list;
    • A block is allocated directly ,

• If not, go to the next step, query $n+3rd$ order page block;