| ===================== |
| CMA Debugfs Interface |
| ===================== |
| |
| The CMA debugfs interface is useful to retrieve basic information out of the |
| different CMA areas and to test allocation/release in each of the areas. |
| |
| Each CMA zone represents a directory under <debugfs>/cma/, indexed by the |
| kernel's CMA index. So the first CMA zone would be: |
| |
| <debugfs>/cma/cma-0 |
| |
| The structure of the files created under that directory is as follows: |
| |
| - [RO] base_pfn: The base PFN (Page Frame Number) of the zone. |
| - [RO] count: Amount of memory in the CMA area. |
| - [RO] order_per_bit: Order of pages represented by one bit. |
| - [RO] bitmap: The bitmap of page states in the zone. |
| - [WO] alloc: Allocate N pages from that CMA area. For example:: |
| |
| echo 5 > <debugfs>/cma/cma-2/alloc |
| |
| would try to allocate 5 pages from the cma-2 area. |
| |
| - [WO] free: Free N pages from that CMA area, similar to the above. |
