On Mon, Jan 23, 2017 at 2:05 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Mon, 2017-01-23 at 13:46 -0800, Xiangning Yu wrote: >> On Mon, Jan 23, 2017 at 12:56 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote: >> > On Mon, Jan 23, 2017 at 10:46 AM, Xiangning Yu <yuxiangn...@gmail.com> >> > wrote: >> >> Hi netdev folks, >> >> >> >> It looks like we call dev_forward_skb() in veth_xmit(), which calls >> >> netif_rx() eventually. >> >> >> >> While netif_rx() will enqueue the skb to the CPU RX backlog before the >> >> actual processing takes place. So, this actually means a TX skb has to >> >> wait some un-related RX skbs to finish. And this will happen twice for >> >> a single ping, because the veth device always works as a pair? >> > >> > For me it is more like for the completeness of network stack of each >> > netns. The /proc net.core.netdev_max_backlog etc. are per netns, which >> > means each netns, as an independent network stack, should respect it >> > too. >> > >> > Since you care about latency, why not tune net.core.dev_weight for your >> > own netns? >> >> I haven't tried that yet, thank you for the hint! Though normally one >> of the veth device will be in the global namespace. > > Well, per cpu backlog are not per net ns, but per cpu.
Right, they all point to a same weight_p. But weight_p itself is not per cpu, softnet_data is. However, if a container uses cpuset and netns for isolations, per cpu will turn into per netns. The point of network stack completeness still stands.
