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Right now dynamic reserved memory regions are allocated either
bottom-up or top-down, depending on the memblock setting of the
architecture. This is fine when the address is arbitrary. However,
when using "alloc-ranges" the regions are often placed somewhere
in the middle of (free) RAM, even if the range starts or ends next
to another (static) reservation.
Try to detect this situation, and choose explicitly between bottom-up
or top-down to allocate the memory close to the other reservations:
1. If the "alloc-range" starts at the end or inside an existing
reservation, use bottom-up.
2. If the "alloc-range" ends at the start or inside an existing
reservation, use top-down.
3. If both or none is the case, keep the current
(architecture-specific) behavior.
There are plenty of edge cases where only a more complex algorithm
would help, but even this simple approach helps in many cases to keep
the reserved memory (and therefore also the free memory) contiguous.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20230510-dt-resv-bottom-up-v2-1-aeb2afc8ac25@gerhold.net
Signed-off-by: Rob Herring <robh@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.