On Wed, Jun 22, 2016 at 06:50:03PM +0300, Leon Romanovsky wrote: > According to [1] dma_alloc_coherent doesn't allocate from pool, but > calls to the __get_free_page(). Use the source luke! dma_alloc_coherent implementations vary widely. While some indeed use alloc_pages there are various complications, especially on non-x86 architectures, or if the dma mask is not the full 64 bits allowed. > "A DMA pool is an allocation mechanism for small, coherent DMA mappings. > Mappings obtained from dma_alloc_coherent may have a minimum size of one > page." Just because it's not using the dma_pool_* API it could allocate from various resource constrained pools. A trivial example for that is the swiotlb used for address limited devices if no hardware IOMMU is available, but other architectures have even more complicated implementations by default. Take a look at arch/arm/mm/dma-mapping.c:__dma_alloc() for fun. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
