From: Jason Xing <kernelxing@xxxxxxxxxxx> Like in VM using virtio_net, there are not that many machines supporting advanced functions like multi buffer and zerocopy. Using xsk copy mode becomes a default choice. Zerocopy mode has a good feature named multi buffer while copy mode has to transmit skb one by one like normal flows. The latter becomes a half bypass mechanism to some extent compared to thorough bypass plan like DPDK. To avoid much consumption in kernel as much as possible, then bulk/batch xmit plan is proposed. The thought of batch xmit is to aggregate packets in a certain small group like GSO/GRO and then read/allocate/build/send them in different loops. Experiments: 1) Tested on virtio_net on Tencent Cloud. copy mode: 767,743 pps batch mode: 1,055,201 pps (+37.4%) xmit.more: 940,398 pps (+22.4%) Side note: 1) another interesting test is if we test with another thread competing the same queue, a 28% increase (from 405,466 pps to 52,1076 pps) can be observed. 2) xmit 'more' item is built on top of batch mode. The number can slightly decrease according to different implementations in host. 2) Tested on i40e at 10Gb/sec. copy mode: 1,109,754 pps batch mode: 2,393,498 pps (+115.6%) xmit.more: 3,024,110 pps (+172.5%) zc mode: 14,879,414 pps [2]: ./xdpsock -i eth1 -t -S -s 64 It's worth mentioning batch process might bring high latency in certain cases like shortage of memroy. So I didn't turn it as the default feature for copy mode. The recommended value is 32. --- V2 Link: https://lore.kernel.org/all/20250811131236.56206-1-kerneljasonxing@xxxxxxxxx/ 1. add xmit.more sub-feature (Jesper) 2. add kmem_cache_alloc_bulk (Jesper and Maciej) Jason Xing (9): xsk: introduce XDP_GENERIC_XMIT_BATCH setsockopt xsk: add descs parameter in xskq_cons_read_desc_batch() xsk: introduce locked version of xskq_prod_write_addr_batch xsk: extend xsk_build_skb() to support passing an already allocated skb xsk: add xsk_alloc_batch_skb() to build skbs in batch xsk: add direct xmit in batch function xsk: support batch xmit main logic xsk: support generic batch xmit in copy mode xsk: support dynamic xmit.more control for batch xmit Documentation/networking/af_xdp.rst | 11 ++ include/linux/netdevice.h | 3 + include/net/xdp_sock.h | 10 ++ include/uapi/linux/if_xdp.h | 1 + net/core/dev.c | 21 +++ net/core/skbuff.c | 103 ++++++++++++++ net/xdp/xsk.c | 200 ++++++++++++++++++++++++++-- net/xdp/xsk_queue.h | 29 +++- tools/include/uapi/linux/if_xdp.h | 1 + 9 files changed, 360 insertions(+), 19 deletions(-) -- 2.41.3
