Commit 17e0db82 authored by Sasha Levin's avatar Sasha Levin Committed by Linus Torvalds

cma: debug: document new debugfs interface

Document the structure and files under the new debugfs interface.
Signed-off-by: default avatarSasha Levin <>
Cc: Joonsoo Kim <>
Cc: Konrad Rzeszutek Wilk <>
Cc: Laura Abbott <>
Cc: Marek Szyprowski <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 875abdb6
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:
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.
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