Documentation/admin-guide/mm/cma_debugfs.rst

Source file repositories/reference/linux-study-clean/Documentation/admin-guide/mm/cma_debugfs.rst

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Linux kernel
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Documentation/admin-guide/mm/cma_debugfs.rst
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.rst
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Support Tooling And Documentation
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Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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=====================
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 CMA area.
        This is the same as ranges/0/base_pfn.
 - [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 allocated pages in the area.
        This is the same as ranges/0/base_pfn.
 - [RO] ranges/N/base_pfn: The base PFN of contiguous range N
        in the CMA area.
 - [RO] ranges/N/bitmap: The bit map of allocated pages in
        range N in the CMA area.
 - [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.

Annotation

Implementation Notes