[PATCHv2 0/4] The Contiguous Memory Allocator

From: Michal Nazarewicz
Date: Mon Jul 26 2010 - 10:10:35 EST

Hello everyone,

The following patchset implements a Contiguous Memory Allocator. For
those who have not yet stumbled across CMA an excerpt from

The Contiguous Memory Allocator (CMA) is a framework, which allows
setting up a machine-specific configuration for physically-contiguous
memory management. Memory for devices is then allocated according
to that configuration.

The main role of the framework is not to allocate memory, but to
parse and manage memory configurations, as well as to act as an
in-between between device drivers and pluggable allocators. It is
thus not tied to any memory allocation method or strategy.

For more information please refer to the second patch from the
patchset which contains the documentation.

This is the second version of the patchset. All of the changes are
concentrated in the second patch -- the other patches are almost

Major observable changes are:

1. The "cma_map" command line have been removed. In exchange, a SysFS
entry has been created under kernel/mm/contiguous.

The configuration strings passed to CMA are now called attributes
in the documentation.

The intended way of specifying the attributes is
a cma_set_defaults() function called by platform initialisation
code. "regions" attribute (the string specified by "cma" command
line parameter) can be overwritten with command line parameter; the
other attributes can be changed during run-time using the SysFS

(I still believe that the other attributes should have their own
command line arguments as well but since they posed a lot of
controversy (and many stopped reading after encountering them)
"cma_map" have been removed.)

2. The behaviour of the "map" attribute has been modified slightly.
Currently, if no rule matches given device it is assigned regions
specified by the "asterisk" attribute. It is by default built from
the region names given in "regions" attribute.

This also means that if no "map" is specified all devices use all
the regions specified in the "regions" attribute. This should be
a handy default.

3. Devices can register private regions as well as regions that can be
shared but are not reserved using standard CMA mechanisms.
A private region has no name and can be accessed only by devices
that have the pointer to it.

Moreover, if device manages to run its code early enough it can
register an "early region". An early region is one memory has not
been reserved for. At one point, platform initialisation code
reserves memory for all registered early regions and if this
succeeds those regions are registered as normal regions that can be
used with the standard API. This may be handy for devices that
need some private region but don't want to worry about reserving

4. The way allocators are registered has changed. Currently,
a cma_allocator_register() function is used for that purpose.
Moreover, allocators are attached to regions the first time memory
is registered from the region or when allocator is registered which
means that allocators can be dynamic modules that are loaded after
the kernel booted (of course, it won't be possible to allocate
a chunk of memory from a region if allocator is not loaded).

Index of new functions:

+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions, size_t size, dma_addr_t alignment)

+static inline int
+cma_info_about(struct cma_info *info, const const char *regions)

+int __must_check cma_region_register(struct cma_region *reg);

+dma_addr_t __must_check
+cma_alloc_from_region(struct cma_region *reg,
+ size_t size, dma_addr_t alignment);

+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions,
+ size_t size, dma_addr_t alignment);

+int cma_allocator_register(struct cma_allocator *alloc);

The patches in the patchset include:

Michal Nazarewicz (4):
lib: rbtree: rb_root_init() function added

The rb_root_init() function initialises an RB tree with a single
node placed in the root. This is more convenient then
initialising an empty tree and then adding an element.

mm: cma: Contiguous Memory Allocator added

This patch is the main patchset that implements the CMA framework
including the best-fit allocator. It also adds a documentation.

mm: cma: Test device and application added

This patch adds a misc device that works as a proxy to the CMA
framework and a simple testing application. This lets one test
the whole framework from user space as well as reply an recorded
allocate/free sequence.

arm: Added CMA to Aquila and Goni

This patch adds the CMA platform initialisation code to two ARM
platforms. It serves as an example of how this is achieved.

Documentation/00-INDEX | 2 +
.../ABI/testing/sysfs-kernel-mm-contiguous | 9 +
Documentation/contiguous-memory.txt | 646 +++++++++++
Documentation/kernel-parameters.txt | 4 +
arch/arm/mach-s5pv210/mach-aquila.c | 13 +
arch/arm/mach-s5pv210/mach-goni.c | 13 +
drivers/misc/Kconfig | 8 +
drivers/misc/Makefile | 1 +
drivers/misc/cma-dev.c | 184 +++
include/linux/cma.h | 475 ++++++++
include/linux/rbtree.h | 11 +
mm/Kconfig | 34 +
mm/Makefile | 3 +
mm/cma-best-fit.c | 407 +++++++
mm/cma.c | 1170 ++++++++++++++++++++
tools/cma/cma-test.c | 373 +++++++
16 files changed, 3353 insertions(+), 0 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-contiguous
create mode 100644 Documentation/contiguous-memory.txt
create mode 100644 drivers/misc/cma-dev.c
create mode 100644 include/linux/cma.h
create mode 100644 mm/cma-best-fit.c
create mode 100644 mm/cma.c
create mode 100644 tools/cma/cma-test.c

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