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| -rw-r--r-- | Documentation/cma/debugfs.txt | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/cma/debugfs.txt b/Documentation/cma/debugfs.txt new file mode 100644 index 000000000000..6cef20a8cedc --- /dev/null +++ b/Documentation/cma/debugfs.txt @@ -0,0 +1,21 @@ +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. |