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Message-ID: <CALDO+SYXo8NJcmLs0BoqXBHwk=wpY70WiuvG4OO73RrpOt9qzA@mail.gmail.com> Date: Mon, 27 Feb 2023 08:01:11 -0800 From: William Tu <u9012063@...il.com> To: Alexander Lobakin <aleksander.lobakin@...el.com> Cc: netdev@...r.kernel.org, jsankararama@...are.com, gyang@...are.com, doshir@...are.com, alexander.duyck@...il.com, alexandr.lobakin@...el.com, bang@...are.com, maciej.fijalkowski@...el.com, witu@...dia.com, Yifeng Sun <yifengs@...are.com>, Alexander Duyck <alexanderduyck@...com> Subject: Re: [RFC PATCH net-next v17] vmxnet3: Add XDP support. On Thu, Feb 23, 2023 at 7:24 AM Alexander Lobakin <aleksander.lobakin@...el.com> wrote: > > From: William Tu <u9012063@...il.com> > Date: Mon, 20 Feb 2023 20:35:47 -0800 > > > The patch adds native-mode XDP support: XDP DROP, PASS, TX, and REDIRECT. > > [...] > > > +static int > > +vmxnet3_xdp_set(struct net_device *netdev, struct netdev_bpf *bpf, > > + struct netlink_ext_ack *extack) > > +{ > > + struct vmxnet3_adapter *adapter = netdev_priv(netdev); > > + struct bpf_prog *new_bpf_prog = bpf->prog; > > + struct bpf_prog *old_bpf_prog; > > + bool need_update; > > + bool running; > > + int err; > > + > > + if (new_bpf_prog && netdev->mtu > VMXNET3_XDP_MAX_MTU) { > > + NL_SET_ERR_MSG_MOD(extack, "MTU too large for XDP"); > > Minor: we now have NL_SET_ERR_MSG_FMT_MOD(), so you could even print to > user what the maximum MTU you support for XDP is. good idea, will use it. > > > + return -EOPNOTSUPP; > > + } > > + > > + if (adapter->netdev->features & NETIF_F_LRO) { > > + NL_SET_ERR_MSG_MOD(extack, "LRO is not supported with XDP"); > > + adapter->netdev->features &= ~NETIF_F_LRO; > > + } > > + > > + old_bpf_prog = rcu_dereference(adapter->xdp_bpf_prog); > > + if (!new_bpf_prog && !old_bpf_prog) > > + return 0; > > + > > + running = netif_running(netdev); > > + need_update = !!old_bpf_prog != !!new_bpf_prog; > > + > > + if (running && need_update) > > + vmxnet3_quiesce_dev(adapter); > > [...] > > > + bpf_warn_invalid_xdp_action(rq->adapter->netdev, prog, act); > > + fallthrough; > > + case XDP_ABORTED: > > + trace_xdp_exception(rq->adapter->netdev, prog, act); > > + rq->stats.xdp_aborted++; > > + break; > > + case XDP_DROP: > > + rq->stats.xdp_drops++; > > + break; > > + } > > + > > + page_pool_recycle_direct(rq->page_pool, page); > > You can speed up stuff a bit here. recycle_direct() takes ->max_len to > sync DMA for device when recycling. You can use page_pool_put_page() and > specify the actual length which needs to be synced. This is a bit > tricky, but some systems have incredibly expensive DMA synchronization > and every byte counts there. > "Tricky" because you can't specify the original frame size here and ATST > can't specify the current xdp.data_end - xdp.data. As xdp.data may grow > to both left and right, the same with .data_end. So what you basically > need is the following: > > sync_len = max(orig_len, > xdp.data_end - xdp.data_hard_start - page_pool->p.offset) > > Because we don't care about the data between data_hard_start and > p.offset -- hardware doesn't touch it. But we care about the whole area > that might've been touched to the right of it. > > Anyway, up to you. On server x86_64 platforms DMA sync is usually a noop. Thanks a lot! Actually at hypersor side we noticed that DMA sync is pretty expensive, that's why we have dataring as optimization (no DMA sync) So it might worth doing it and I will try and see if there is any performance difference! (but not the next version) > > > + > > + return act; > > +} > > [...] > > > +static inline bool vmxnet3_xdp_enabled(struct vmxnet3_adapter *adapter) > > +{ > > + return !!rcu_access_pointer(adapter->xdp_bpf_prog); > > +} > > + > > +#endif > > I feel good with the rest of the patch, thanks! Glad to see all the > feedback addressed when applicable. > > Olek Thanks! William
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