mm: cma: adjust address limit to avoid hitting low/high memory boundary

Linux Kernel / Linux Kernel - Marek Szyprowski [samsung.com] - 9 October 2014 21:25 EDT

Russell King recently noticed that limiting default CMA region only to low memory on ARM architecture causes serious memory management issues with machines having a lot of memory (which is mainly available as high memory). More information can be found the following thread: http://thread.gmane.org/gmane.linux.ports.arm.kernel/348441/

Those two patches removes this limit letting kernel to put default CMA region into high memory when this is possible (there is enough high memory available and architecture specific DMA limit fits).

This should solve strange OOM issues on systems with lots of RAM (i.e. >1GiB) and large (>256M) CMA area.

This patch (of 2):

Automatically allocated regions should not cross low/high memory boundary, because such regions cannot be later correctly initialized due to spanning across two memory zones. This patch adds a check for this case and a simple code for moving region to low memory if automatically selected address might not fit completely into high memory.

f7426b9 mm: cma: adjust address limit to avoid hitting low/high memory boundary
mm/cma.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

Upstream: git.kernel.org


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