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Documentation / cma / debugfs.txt




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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.

1	The CMA debugfs interface is useful to retrieve basic information out of the
2	different CMA areas and to test allocation/release in each of the areas.
3	
4	Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
5	kernel's CMA index. So the first CMA zone would be:
6	
7		<debugfs>/cma/cma-0
8	
9	The 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	
19	would 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.
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