aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/admin-guide/mm/cma_debugfs.rst
blob: 7367e6294ef6ee18564bca158ac99faeace03a5e (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
=====================
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 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.