1===================== 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 area represents a directory under <debugfs>/cma/, represented by 9its CMA name like below: 10 11 <debugfs>/cma/<cma_name> 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_name>/alloc 22 23would try to allocate 5 pages from the 'cma_name' area. 24 25 - [WO] free: Free N pages from that CMA area, similar to the above. 26