Re: [PATCH 2/4] mm: cma: Contiguous Memory Allocator added

[Zach Pfeffer]

On Tue, Jul 20, 2010 at 05:51:25PM +0200, Michal Nazarewicz wrote:
> The Contiguous Memory Allocator framework is a set of APIs for
> allocating physically contiguous chunks of memory.
> 
> Various chips require contiguous blocks of memory to operate.  Those
> chips include devices such as cameras, hardware video decoders and
> encoders, etc.
> 
> The code is highly modular and customisable to suit the needs of
> various users.  Set of regions reserved for CMA can be configured on
> run-time and it is easy to add custom allocator algorithms if one
> has such need.
> 
> Signed-off-by: Michal Nazarewicz <m.nazarewicz@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Reviewed-by: Pawel Osciak <p.osciak@xxxxxxxxxxx>
> ---
>  Documentation/cma.txt               |  435 +++++++++++++++++++
>  Documentation/kernel-parameters.txt |    7 +
>  include/linux/cma-int.h             |  183 ++++++++
>  include/linux/cma.h                 |   92 ++++
>  mm/Kconfig                          |   41 ++
>  mm/Makefile                         |    3 +
>  mm/cma-allocators.h                 |   42 ++
>  mm/cma-best-fit.c                   |  360 ++++++++++++++++
>  mm/cma.c                            |  778 +++++++++++++++++++++++++++++++++++
>  9 files changed, 1941 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/cma.txt
>  create mode 100644 include/linux/cma-int.h
>  create mode 100644 include/linux/cma.h
>  create mode 100644 mm/cma-allocators.h
>  create mode 100644 mm/cma-best-fit.c
>  create mode 100644 mm/cma.c
> 
> diff --git a/Documentation/cma.txt b/Documentation/cma.txt
> new file mode 100644
> index 0000000..7edc20a
> --- /dev/null
> +++ b/Documentation/cma.txt
> @@ -0,0 +1,435 @@
> +                                                             -*- org -*-
> +
> +* Contiguous Memory Allocator
> +
> +   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.
> +

This topic seems very hot lately. I recently sent out a few RFCs that
implement something called a Virtual Contiguous Memory Manager that
does what this patch does, and works for IOMMU and works for CPU
mappings. It also does multihomed memory targeting (use physical set 1
memory for A allocations and use physical memory set 2 for B
allocations). Check out:

mm: iommu: An API to unify IOMMU, CPU and device memory management
mm: iommu: A physical allocator for the VCMM
mm: iommu: The Virtual Contiguous Memory Manager

It unifies IOMMU and physical mappings by creating a one-to-one
software IOMMU for all devices that map memory physically.

It looks like you've got some good ideas though. Perhaps we can
leverage each other's work.
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