cma_debugfs.rst (894B)
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 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.