[Linaro-mm-sig] Re: [PATCH v2 0/5] Introduce DMA_HEAP_ALLOC_AND_READ_FILE heap flag

On Tue, Jul 30, 2024 at 03:57:44PM +0800, Huan Yang wrote:

UDMA-BUF step:

1. memfd_create
2. open file(buffer/direct)
3. udmabuf create
4. mmap memfd
5. read file into memfd vaddr

Yeah this is really slow and the worst way to do it. You absolutely want to start _all_ the io before you start creating the dma-buf, ideally with everything running in parallel. But just starting the direct I/O with async and then creating the umdabuf should be a lot faster and avoid needlessly serialization operations.

The other issue is that the mmap has some overhead, but might not be too bad. -Sima