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Diffstat (limited to 'Documentation/admin-guide/mm/cma_debugfs.rst')
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diff --git a/Documentation/admin-guide/mm/cma_debugfs.rst b/Documentation/admin-guide/mm/cma_debugfs.rst new file mode 100644 index 000000000000..4120e9cb0cd5 --- /dev/null +++ b/Documentation/admin-guide/mm/cma_debugfs.rst @@ -0,0 +1,31 @@ +===================== +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: + + <debugfs>/cma/<cma_name> + +The structure of the files created under that directory is as follows: + + - [RO] base_pfn: The base PFN (Page Frame Number) of the CMA area. + This is the same as ranges/0/base_pfn. + - [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 allocated pages in the area. + This is the same as ranges/0/base_pfn. + - [RO] ranges/N/base_pfn: The base PFN of contiguous range N + in the CMA area. + - [RO] ranges/N/bitmap: The bit map of allocated pages in + range N in the CMA area. + - [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. |