Based on kernel version
5.9. Page generated on
2020-10-14 09:35 EST.
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===================== 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.