Re: [PATCH v2 0/5] Introduce DMA_HEAP_ALLOC_AND_READ_FILE heap flag

Daniel Vetter
2024-07-30T08:56:35Z

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
--
Daniel Vetter
Software Engineer, Intel Corporation