On Wed, Mar 25, 2020 at 11:02 AM Gaul, Maximilian <maximilian.gaul@xxxxxx> wrote: > > On Wed, Mar 25, 2020 at 10:41 AM Karlsson, Magnus > <magnus.karlsson@xxxxxxxxx> wrote: > > > On Wed, Mar 25, 2020 at 10:04 AM Gaul, Maximilian > > <maximilian.gaul@xxxxxx> wrote: > > > > > > I am running a Multi-AF-XDP-Socket approach per RX-Queue (using Shared Umem). > > > > > > Unfortunately I am noticing, that at around 650k pps, the *ksoftirqd*-thread of that RX-Queue ramps up to 100% thus leading to packet loss. > > > I tried setting *XDP_USE_NEED_WAKEUP* on *xsk_socket_cfg.bind_flags* but those bind_flags are only taken into account if *umem->refcount > 1* (libbpf/xsk.c - xsk_socket__create()). > > > As far as I understand this correctly, only the first socket is able to set *XDP_USE_NEED_WAKEUP* because for all sockets after, *umem->refcount* is going to be at least 2. > > > > Yes, the other sockets just inherit the settings of the first one. > > > > Are you using the SKB mode? What is your packet size? Sounds like a > > low number unless you have large packets and are using the SKB mode. > > > > These are the flags I set right before calling `xsk_socket__create`: > > xsk_socket_cfg.xdp_flags = cfg->xdp_flags | XDP_FLAGS_DRV_MODE | XDP_ZEROCOPY; > xsk_socket_cfg.bind_flags = cfg->xsk_bind_flags | XDP_USE_NEED_WAKEUP; XDP_ZEROCOPY is a bind flag not an XDP flag, so please move it there. If you get an error when you have it set, it means that your setup does not support zero-copy for some reason. Check what kernel version you are using and the the driver you are using supports zero-copy. I believe you need to use a queue id>=32 in the Mellanox driver for it to work in zero-copy mode. Below 32, you will get copy mode. > Packet size is around 1492 bytes. Seems that you are using SKB mode then, not zero-copy. /Magnus > Just to make sure: Those 650k packets are arriving on the same RX-Queue (even though this NIC has multiple RX-Queues I want to test maximum bandwith for a single RX-Queue). > > > > I didn't observe a dramatic change as I've hoped to. Are there some other ways to reduce interrupt load (user-space application and ksoftirq are already running on different CPUs)? > > > > The need_wakeup flag has a big impact when you run the softirq and the > > application thread on the same core. When using two cores for this, it > > has less of an impact. > > > > /Magnus > > > > > NIC: Mellanox Technologies MT27800 > > > > > > Best regards > > > > > > Max > > > >
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