Jakub Kicinski wrote: > On Wed, 19 Aug 2020 22:22:23 +0200 Lorenzo Bianconi wrote: > > > On Wed, 19 Aug 2020 15:13:51 +0200 Lorenzo Bianconi wrote: > > > > Enable the capability to receive jumbo frames even if the interface is > > > > running in XDP mode > > > > > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> > > > > > > Hm, already? Is all the infra in place? Or does it not imply > > > multi-buffer. > > > > with this series mvneta supports xdp multi-buff on both rx and tx sides (XDP_TX > > and ndo_xpd_xmit()) so we can remove MTU limitation. > > Is there an API for programs to access the multi-buf frames? Hi Lorenzo, This is not enough to support multi-buffer in my opinion. I have the same comment as Jakub. We need an API to pull in the multiple buffers otherwise we break the ability to parse the packets and that is a hard requirement to me. I don't want to lose visibility to get jumbo frames. At minimum we need a bpf_xdp_pull_data() to adjust pointer. In the skmsg case we use this, bpf_msg_pull_data(u32 start, u32 end, u64 flags) Where start is the offset into the packet and end is the last byte we want to adjust start/end pointers to. This way we can walk pages if we want and avoid having to linearize the data unless the user actual asks us for a block that crosses a page range. Smart users then never do a start/end that crosses a page boundary if possible. I think the same would apply here. XDP by default gives you the first page start/end to use freely. If you need to parse deeper into the payload then you call bpf_msg_pull_data with the byte offsets needed. Also we would want performance numbers to see how good/bad this is compared to the base case. Thanks, John
