[linux-2.6-block.git] / Documentation / cma / debugfs.txt

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.
Commit	Line	Data
17e0db82 SL	1	The CMA debugfs interface is useful to retrieve basic information out of the
	2	different CMA areas and to test allocation/release in each of the areas.
	3
	4	Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
	5	kernel's CMA index. So the first CMA zone would be:
	6
	7	<debugfs>/cma/cma-0
	8
	9	The structure of the files created under that directory is as follows:
	10
	11	- [RO] base_pfn: The base PFN (Page Frame Number) of the zone.
	12	- [RO] count: Amount of memory in the CMA area.
	13	- [RO] order_per_bit: Order of pages represented by one bit.
	14	- [RO] bitmap: The bitmap of page states in the zone.
	15	- [WO] alloc: Allocate N pages from that CMA area. For example:
	16
	17	echo 5 > <debugfs>/cma/cma-2/alloc
	18
	19	would try to allocate 5 pages from the cma-2 area.
	20
	21	- [WO] free: Free N pages from that CMA area, similar to the above.