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 area represents a directory under <debugfs>/cma/, represented by its CMA name like below:
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_name>/alloc
would try to allocate 5 pages from the ‘cma_name’ area.
[WO] free: Free N pages from that CMA area, similar to the above.