Messages in this thread | | | From | Jose Abreu <> | Subject | RE: [PATCH net-next 3/3] net: stmmac: Introducing support for Page Pool | Date | Thu, 4 Jul 2019 10:13:37 +0000 |
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From: Jesper Dangaard Brouer <brouer@redhat.com>
> The page_pool DMA mapping cannot be "kept" when page traveling into the > network stack attached to an SKB. (Ilias and I have a long term plan[1] > to allow this, but you cannot do it ATM).
The reason I recycle the page is this previous call to:
skb_copy_to_linear_data()
So, technically, I'm syncing to CPU the page(s) and then memcpy to a previously allocated SKB ... So it's safe to just recycle the mapping I think.
Its kind of using bounce buffers and I do see performance gain in this (I think the reason is because my setup uses swiotlb for DMA mapping).
Anyway, I'm open to some suggestions on how to improve this ...
> Also remember that the page_pool requires you driver to do the DMA-sync > operation. I see a dma_sync_single_for_cpu(), but I didn't see a > dma_sync_single_for_device() (well, I noticed one getting removed). > (For some HW Ilias tells me that the dma_sync_single_for_device can be > elided, so maybe this can still be correct for you).
My HW just needs descriptors refilled which are in different coherent region so I don't see any reason for dma_sync_single_for_device() ...
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