Messages in this thread | | | Date | Wed, 8 May 2024 21:49:39 -0700 | From | Christoph Hellwig <> | Subject | Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers |
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On Wed, May 08, 2024 at 06:02:14PM +0100, Pavel Begunkov wrote: > Well, the example fell flat, but you don't use dmabuf when there are > no upsides from using it. For instance, when you already have pinned > pages, you're going to use pages, and there are no other refcounting > concerns.
Sure.
> Unless there is an advantage of dmabufs over FOLL_LONGTERM > that I don't know about when used with normal user pages.
The advantages of using a dma-buf over FOLL_LONGTERM are:
a) you pre-dma map, which is a significant performance advantage for IOMMU-based setups b) you support any dma-buf exported and not just user memory. This is primarily important for PCIe P2P, but there might be other useful exporters as well
> > wish io_uring would have just implemented them from the start instead of > > the current fixed buffers that are not quite as useful by not > > pre-mapping DMA and not supporting P2P. > > fdget(dmabuf) would be horrible, I assume that's not the suggestion.
I'm not even sure what you mean with that.
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