1*4882a593Smuzhiyun===================== 2*4882a593SmuzhiyunCMA Debugfs Interface 3*4882a593Smuzhiyun===================== 4*4882a593Smuzhiyun 5*4882a593SmuzhiyunThe CMA debugfs interface is useful to retrieve basic information out of the 6*4882a593Smuzhiyundifferent CMA areas and to test allocation/release in each of the areas. 7*4882a593Smuzhiyun 8*4882a593SmuzhiyunEach CMA zone represents a directory under <debugfs>/cma/, indexed by the 9*4882a593Smuzhiyunkernel's CMA index. So the first CMA zone would be: 10*4882a593Smuzhiyun 11*4882a593Smuzhiyun <debugfs>/cma/cma-0 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunThe structure of the files created under that directory is as follows: 14*4882a593Smuzhiyun 15*4882a593Smuzhiyun - [RO] base_pfn: The base PFN (Page Frame Number) of the zone. 16*4882a593Smuzhiyun - [RO] count: Amount of memory in the CMA area. 17*4882a593Smuzhiyun - [RO] order_per_bit: Order of pages represented by one bit. 18*4882a593Smuzhiyun - [RO] bitmap: The bitmap of page states in the zone. 19*4882a593Smuzhiyun - [WO] alloc: Allocate N pages from that CMA area. For example:: 20*4882a593Smuzhiyun 21*4882a593Smuzhiyun echo 5 > <debugfs>/cma/cma-2/alloc 22*4882a593Smuzhiyun 23*4882a593Smuzhiyunwould try to allocate 5 pages from the cma-2 area. 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun - [WO] free: Free N pages from that CMA area, similar to the above. 26