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CONFIG_CMA_ALIGNMENT: Maximum PAGE_SIZE order of alignment for contiguous buffers

General informations

The Linux kernel configuration item CONFIG_CMA_ALIGNMENT:

Help text

DMA mapping framework by default aligns all buffers to the smallest PAGE_SIZE order which is greater than or equal to the requested buffer size. This works well for buffers up to a few hundreds kilobytes, but for larger buffers it just a memory waste. With this parameter you can specify the maximum PAGE_SIZE order for contiguous buffers. Larger buffers will be aligned only to this specified order. The order is expressed as a power of two multiplied by the PAGE_SIZE.

For example, if your system defaults to 4KiB pages, the order value of 8 means that the buffers will be aligned up to 1MiB only.

If unsure, leave the default value "8".

Hardware

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