Mastering Linux Kernel Development

Contiguous Memory Allocator (CMA)

Albeit with significant overheads, virtually mapped allocations solve the problem of large memory allocations to a greater extent. However, there are a few scenarios that mandate the allocation of physically contiguous buffers. DMA transfers are one such case. Device drivers often find a stringent need for physically contiguous buffer allocations (for setting up DMA transfers), which are carried out through any of the physically contiguous allocators discussed earlier.

However, drivers dealing with specific classes of devices such as multimedia often find themselves searching for huge blocks of contiguous memory. To meet this end, over the years, such drivers have been reserving memory during system boot ...