| Message ID | 20210415135320.4084595-2-liuhangbin@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | xdp: extend xdp_redirect_map with broadcast support | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 7 maintainers not CCed: yhs@fb.com kpsingh@kernel.org hawk@kernel.org andrii@kernel.org songliubraving@fb.com davem@davemloft.net kuba@kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 1 this patch: 1 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 204 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 1 this patch: 1 |
| netdev/header_inline | success | Link |
On Thu, Apr 15, 2021 at 09:53:17PM +0800, Hangbin Liu wrote: > From: Jesper Dangaard Brouer <brouer@redhat.com> > > This changes the devmap XDP program support to run the program when the > bulk queue is flushed instead of before the frame is enqueued. This has > a couple of benefits: > > - It "sorts" the packets by destination devmap entry, and then runs the > same BPF program on all the packets in sequence. This ensures that we > keep the XDP program and destination device properties hot in I-cache. > > - It makes the multicast implementation simpler because it can just > enqueue packets using bq_enqueue() without having to deal with the > devmap program at all. > > The drawback is that if the devmap program drops the packet, the enqueue > step is redundant. However, arguably this is mostly visible in a > micro-benchmark, and with more mixed traffic the I-cache benefit should > win out. The performance impact of just this patch is as follows: > > When bq_xmit_all() is called from bq_enqueue(), another packet will > always be enqueued immediately after, so clearing dev_rx, xdp_prog and > flush_node in bq_xmit_all() is redundant. Move the clear to __dev_flush(), > and only check them once in bq_enqueue() since they are all modified > together. > > Using 10Gb i40e NIC, do XDP_DROP on veth peer, with xdp_redirect_map in > sample/bpf, send pkts via pktgen cmd: > ./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64 > > There are about +/- 0.1M deviation for native testing, the performance > improved for the base-case, but some drop back with xdp devmap prog attached. > > Version | Test | Generic | Native | Native + 2nd xdp_prog > 5.12 rc4 | xdp_redirect_map i40e->i40e | 1.9M | 9.6M | 8.4M > 5.12 rc4 | xdp_redirect_map i40e->veth | 1.7M | 11.7M | 9.8M > 5.12 rc4 + patch | xdp_redirect_map i40e->i40e | 1.9M | 9.8M | 8.0M > 5.12 rc4 + patch | xdp_redirect_map i40e->veth | 1.7M | 12.0M | 9.4M Based on the discussion in v7, a summary of what still needs to be addressed will be useful.
Martin KaFai Lau <kafai@fb.com> writes: > On Thu, Apr 15, 2021 at 09:53:17PM +0800, Hangbin Liu wrote: >> From: Jesper Dangaard Brouer <brouer@redhat.com> >> >> This changes the devmap XDP program support to run the program when the >> bulk queue is flushed instead of before the frame is enqueued. This has >> a couple of benefits: >> >> - It "sorts" the packets by destination devmap entry, and then runs the >> same BPF program on all the packets in sequence. This ensures that we >> keep the XDP program and destination device properties hot in I-cache. >> >> - It makes the multicast implementation simpler because it can just >> enqueue packets using bq_enqueue() without having to deal with the >> devmap program at all. >> >> The drawback is that if the devmap program drops the packet, the enqueue >> step is redundant. However, arguably this is mostly visible in a >> micro-benchmark, and with more mixed traffic the I-cache benefit should >> win out. The performance impact of just this patch is as follows: >> >> When bq_xmit_all() is called from bq_enqueue(), another packet will >> always be enqueued immediately after, so clearing dev_rx, xdp_prog and >> flush_node in bq_xmit_all() is redundant. Move the clear to __dev_flush(), >> and only check them once in bq_enqueue() since they are all modified >> together. (side note, while we're modifying the commit message, this paragraph should probably be moved to the end) >> Using 10Gb i40e NIC, do XDP_DROP on veth peer, with xdp_redirect_map in >> sample/bpf, send pkts via pktgen cmd: >> ./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64 >> >> There are about +/- 0.1M deviation for native testing, the performance >> improved for the base-case, but some drop back with xdp devmap prog attached. >> >> Version | Test | Generic | Native | Native + 2nd xdp_prog >> 5.12 rc4 | xdp_redirect_map i40e->i40e | 1.9M | 9.6M | 8.4M >> 5.12 rc4 | xdp_redirect_map i40e->veth | 1.7M | 11.7M | 9.8M >> 5.12 rc4 + patch | xdp_redirect_map i40e->i40e | 1.9M | 9.8M | 8.0M >> 5.12 rc4 + patch | xdp_redirect_map i40e->veth | 1.7M | 12.0M | 9.4M > Based on the discussion in v7, a summary of what still needs to be > addressed will be useful. That's fair. How about we add a paragraph like this (below the one I just suggested above that we move to the end): This change also has the side effect of extending the lifetime of the RCU-protected xdp_prog that lives inside the devmap entries: Instead of just living for the duration of the XDP program invocation, the reference now lives all the way until the bq is flushed. This is safe because the bq flush happens at the end of the NAPI poll loop, so everything happens between a local_bh_disable()/local_bh_enable() pair. However, this is by no means obvious from looking at the call sites; in particular, some drivers have an additional rcu_read_lock() around only the XDP program invocation, which only confuses matters further. Clearing this up will be done in a separate patch series.
On Tue, Apr 20, 2021 at 10:56:56PM +0200, Toke Høiland-Jørgensen wrote: > Martin KaFai Lau <kafai@fb.com> writes: > > > On Thu, Apr 15, 2021 at 09:53:17PM +0800, Hangbin Liu wrote: > >> From: Jesper Dangaard Brouer <brouer@redhat.com> > >> > >> This changes the devmap XDP program support to run the program when the > >> bulk queue is flushed instead of before the frame is enqueued. This has > >> a couple of benefits: > >> > >> - It "sorts" the packets by destination devmap entry, and then runs the > >> same BPF program on all the packets in sequence. This ensures that we > >> keep the XDP program and destination device properties hot in I-cache. > >> > >> - It makes the multicast implementation simpler because it can just > >> enqueue packets using bq_enqueue() without having to deal with the > >> devmap program at all. > >> > >> The drawback is that if the devmap program drops the packet, the enqueue > >> step is redundant. However, arguably this is mostly visible in a > >> micro-benchmark, and with more mixed traffic the I-cache benefit should > >> win out. The performance impact of just this patch is as follows: > >> > >> When bq_xmit_all() is called from bq_enqueue(), another packet will > >> always be enqueued immediately after, so clearing dev_rx, xdp_prog and > >> flush_node in bq_xmit_all() is redundant. Move the clear to __dev_flush(), > >> and only check them once in bq_enqueue() since they are all modified > >> together. > > (side note, while we're modifying the commit message, this paragraph > should probably be moved to the end) > > >> Using 10Gb i40e NIC, do XDP_DROP on veth peer, with xdp_redirect_map in > >> sample/bpf, send pkts via pktgen cmd: > >> ./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64 > >> > >> There are about +/- 0.1M deviation for native testing, the performance > >> improved for the base-case, but some drop back with xdp devmap prog attached. > >> > >> Version | Test | Generic | Native | Native + 2nd xdp_prog > >> 5.12 rc4 | xdp_redirect_map i40e->i40e | 1.9M | 9.6M | 8.4M > >> 5.12 rc4 | xdp_redirect_map i40e->veth | 1.7M | 11.7M | 9.8M > >> 5.12 rc4 + patch | xdp_redirect_map i40e->i40e | 1.9M | 9.8M | 8.0M > >> 5.12 rc4 + patch | xdp_redirect_map i40e->veth | 1.7M | 12.0M | 9.4M > > Based on the discussion in v7, a summary of what still needs to be > > addressed will be useful. > > That's fair. How about we add a paragraph like this (below the one I > just suggested above that we move to the end): > > This change also has the side effect of extending the lifetime of the > RCU-protected xdp_prog that lives inside the devmap entries: Instead of > just living for the duration of the XDP program invocation, the > reference now lives all the way until the bq is flushed. This is safe > because the bq flush happens at the end of the NAPI poll loop, so > everything happens between a local_bh_disable()/local_bh_enable() pair. > However, this is by no means obvious from looking at the call sites; in > particular, some drivers have an additional rcu_read_lock() around only > the XDP program invocation, which only confuses matters further. > Clearing this up will be done in a separate patch series. lgtm
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index aa516472ce46..3980fb3bfb09 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -57,6 +57,7 @@ struct xdp_dev_bulk_queue { struct list_head flush_node; struct net_device *dev; struct net_device *dev_rx; + struct bpf_prog *xdp_prog; unsigned int count; }; @@ -326,22 +327,71 @@ bool dev_map_can_have_prog(struct bpf_map *map) return false; } +static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog, + struct xdp_frame **frames, int n, + struct net_device *dev) +{ + struct xdp_txq_info txq = { .dev = dev }; + struct xdp_buff xdp; + int i, nframes = 0; + + for (i = 0; i < n; i++) { + struct xdp_frame *xdpf = frames[i]; + u32 act; + int err; + + xdp_convert_frame_to_buff(xdpf, &xdp); + xdp.txq = &txq; + + act = bpf_prog_run_xdp(xdp_prog, &xdp); + switch (act) { + case XDP_PASS: + err = xdp_update_frame_from_buff(&xdp, xdpf); + if (unlikely(err < 0)) + xdp_return_frame_rx_napi(xdpf); + else + frames[nframes++] = xdpf; + break; + default: + bpf_warn_invalid_xdp_action(act); + fallthrough; + case XDP_ABORTED: + trace_xdp_exception(dev, xdp_prog, act); + fallthrough; + case XDP_DROP: + xdp_return_frame_rx_napi(xdpf); + break; + } + } + return nframes; /* sent frames count */ +} + static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags) { struct net_device *dev = bq->dev; - int sent = 0, err = 0; + int sent = 0, drops = 0, err = 0; + unsigned int cnt = bq->count; + int to_send = cnt; int i; - if (unlikely(!bq->count)) + if (unlikely(!cnt)) return; - for (i = 0; i < bq->count; i++) { + for (i = 0; i < cnt; i++) { struct xdp_frame *xdpf = bq->q[i]; prefetch(xdpf); } - sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags); + if (bq->xdp_prog) { + to_send = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev); + if (!to_send) + goto out; + + drops = cnt - to_send; + } + + sent = dev->netdev_ops->ndo_xdp_xmit(dev, to_send, bq->q, flags); if (sent < 0) { /* If ndo_xdp_xmit fails with an errno, no frames have * been xmit'ed. @@ -353,13 +403,13 @@ static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags) /* If not all frames have been transmitted, it is our * responsibility to free them */ - for (i = sent; unlikely(i < bq->count); i++) + for (i = sent; unlikely(i < to_send); i++) xdp_return_frame_rx_napi(bq->q[i]); - trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, bq->count - sent, err); - bq->dev_rx = NULL; +out: + drops = cnt - sent; bq->count = 0; - __list_del_clearprev(&bq->flush_node); + trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, drops, err); } /* __dev_flush is called from xdp_do_flush() which _must_ be signaled @@ -377,8 +427,12 @@ void __dev_flush(void) struct list_head *flush_list = this_cpu_ptr(&dev_flush_list); struct xdp_dev_bulk_queue *bq, *tmp; - list_for_each_entry_safe(bq, tmp, flush_list, flush_node) + list_for_each_entry_safe(bq, tmp, flush_list, flush_node) { bq_xmit_all(bq, XDP_XMIT_FLUSH); + bq->dev_rx = NULL; + bq->xdp_prog = NULL; + __list_del_clearprev(&bq->flush_node); + } } /* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or @@ -401,7 +455,7 @@ static void *__dev_map_lookup_elem(struct bpf_map *map, u32 key) * Thus, safe percpu variable access. */ static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf, - struct net_device *dev_rx) + struct net_device *dev_rx, struct bpf_prog *xdp_prog) { struct list_head *flush_list = this_cpu_ptr(&dev_flush_list); struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq); @@ -412,18 +466,22 @@ static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf, /* Ingress dev_rx will be the same for all xdp_frame's in * bulk_queue, because bq stored per-CPU and must be flushed * from net_device drivers NAPI func end. + * + * Do the same with xdp_prog and flush_list since these fields + * are only ever modified together. */ - if (!bq->dev_rx) + if (!bq->dev_rx) { bq->dev_rx = dev_rx; + bq->xdp_prog = xdp_prog; + list_add(&bq->flush_node, flush_list); + } bq->q[bq->count++] = xdpf; - - if (!bq->flush_node.prev) - list_add(&bq->flush_node, flush_list); } static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp, - struct net_device *dev_rx) + struct net_device *dev_rx, + struct bpf_prog *xdp_prog) { struct xdp_frame *xdpf; int err; @@ -439,42 +497,14 @@ static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp, if (unlikely(!xdpf)) return -EOVERFLOW; - bq_enqueue(dev, xdpf, dev_rx); + bq_enqueue(dev, xdpf, dev_rx, xdp_prog); return 0; } -static struct xdp_buff *dev_map_run_prog(struct net_device *dev, - struct xdp_buff *xdp, - struct bpf_prog *xdp_prog) -{ - struct xdp_txq_info txq = { .dev = dev }; - u32 act; - - xdp_set_data_meta_invalid(xdp); - xdp->txq = &txq; - - act = bpf_prog_run_xdp(xdp_prog, xdp); - switch (act) { - case XDP_PASS: - return xdp; - case XDP_DROP: - break; - default: - bpf_warn_invalid_xdp_action(act); - fallthrough; - case XDP_ABORTED: - trace_xdp_exception(dev, xdp_prog, act); - break; - } - - xdp_return_buff(xdp); - return NULL; -} - int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp, struct net_device *dev_rx) { - return __xdp_enqueue(dev, xdp, dev_rx); + return __xdp_enqueue(dev, xdp, dev_rx, NULL); } int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp, @@ -482,12 +512,7 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp, { struct net_device *dev = dst->dev; - if (dst->xdp_prog) { - xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog); - if (!xdp) - return 0; - } - return __xdp_enqueue(dev, xdp, dev_rx); + return __xdp_enqueue(dev, xdp, dev_rx, dst->xdp_prog); } int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,