| Sasha Levin | 17e0db8 | 2015-04-14 15:45:08 -0700 | [diff] [blame] | 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. |