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1The CMA debugfs interface is useful to retrieve basic information out of the
2different CMA areas and to test allocation/release in each of the areas.
3
4Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
5kernel's CMA index. So the first CMA zone would be:
6
7 <debugfs>/cma/cma-0
8
9The structure of the files created under that directory is as follows:
10
11 - [RO] base_pfn: The base PFN (Page Frame Number) of the zone.
12 - [RO] count: Amount of memory in the CMA area.
13 - [RO] order_per_bit: Order of pages represented by one bit.
14 - [RO] bitmap: The bitmap of page states in the zone.
15 - [WO] alloc: Allocate N pages from that CMA area. For example:
16
17 echo 5 > <debugfs>/cma/cma-2/alloc
18
19would try to allocate 5 pages from the cma-2 area.
20
21 - [WO] free: Free N pages from that CMA area, similar to the above.