blob: 4e06ffabd78ae370c6534e1a71a419226afa9b6f [file] [log] [blame]
b.liue9582032025-04-17 19:18:16 +08001=====================
2CMA Debugfs Interface
3=====================
4
5The CMA debugfs interface is useful to retrieve basic information out of the
6different CMA areas and to test allocation/release in each of the areas.
7
8Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
9kernel's CMA index. So the first CMA zone would be:
10
11 <debugfs>/cma/cma-0
12
13The structure of the files created under that directory is as follows:
14
15 - [RO] base_pfn: The base PFN (Page Frame Number) of the zone.
16 - [RO] count: Amount of memory in the CMA area.
17 - [RO] order_per_bit: Order of pages represented by one bit.
18 - [RO] bitmap: The bitmap of page states in the zone.
19 - [WO] alloc: Allocate N pages from that CMA area. For example::
20
21 echo 5 > <debugfs>/cma/cma-2/alloc
22
23would try to allocate 5 pages from the cma-2 area.
24
25 - [WO] free: Free N pages from that CMA area, similar to the above.