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authorSasha Levin <sasha.levin@oracle.com>2015-04-14 15:45:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-14 16:49:00 -0700
commit17e0db822b00cff96c1b662ac0dc0449cb70e0ec (patch)
treeb503c16809f9e83d63b59f834851660311ced95b
parent875abdb6d43401c745ee8bc6d240f119a601d21f (diff)
downloadlinux-stericsson-17e0db822b00cff96c1b662ac0dc0449cb70e0ec.tar.gz
cma: debug: document new debugfs interface
Document the structure and files under the new debugfs interface. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Laura Abbott <lauraa@codeaurora.org> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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+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.