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.