[bpf-next V2 PATCH 3/3] xdp: split code for map vs non-map redirect
From: Jesper Dangaard Brouer <hidden>
Date: 2018-09-03 12:14:07
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Martin KaFai Lau, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
The compiler does an efficient job of inlining static C functions. Perf top clearly shows that almost everything gets inlined into the function call xdp_do_redirect. The function xdp_do_redirect end-up containing and interleaving the map and non-map redirect code. This is sub-optimal, as it would be strange for an XDP program to use both types of redirect in the same program. The two use-cases are separate, and interleaving the code just cause more instruction-cache pressure. I would like to stress (again) that the non-map variant bpf_redirect is very slow compared to the bpf_redirect_map variant, approx half the speed. Measured with driver i40e the difference is: - map redirect: 13,250,350 pps - non-map redirect: 7,491,425 pps For this reason, the function name of the non-map variant of redirect have been called xdp_do_redirect_slow. This hopefully gives a hint when using perf, that this is not the optimal XDP redirect operating mode. Signed-off-by: Jesper Dangaard Brouer <redacted> --- net/core/filter.c | 52 ++++++++++++++++++++++++++++++---------------------- 1 file changed, 30 insertions(+), 22 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index ec1b4eb0d3d4..7738d1d70154 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -3170,6 +3170,32 @@ static int __bpf_tx_xdp(struct net_device *dev, return 0; } +static noinline int +xdp_do_redirect_slow(struct net_device *dev, struct xdp_buff *xdp, + struct bpf_prog *xdp_prog, struct bpf_redirect_info *ri) +{ + struct net_device *fwd; + u32 index = ri->ifindex; + int err; + + fwd = dev_get_by_index_rcu(dev_net(dev), index); + ri->ifindex = 0; + if (unlikely(!fwd)) { + err = -EINVAL; + goto err; + } + + err = __bpf_tx_xdp(fwd, NULL, xdp, 0); + if (unlikely(err)) + goto err; + + _trace_xdp_redirect(dev, xdp_prog, index); + return 0; +err: + _trace_xdp_redirect_err(dev, xdp_prog, index, err); + return err; +} + static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd, struct bpf_map *map, struct xdp_buff *xdp,
@@ -3264,9 +3290,9 @@ void bpf_clear_redirect_map(struct bpf_map *map) } static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, - struct bpf_prog *xdp_prog, struct bpf_map *map) + struct bpf_prog *xdp_prog, struct bpf_map *map, + struct bpf_redirect_info *ri) { - struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); u32 index = ri->ifindex; void *fwd = NULL; int err;
@@ -3299,29 +3325,11 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp, { struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); struct bpf_map *map = READ_ONCE(ri->map); - struct net_device *fwd; - u32 index = ri->ifindex; - int err; if (likely(map)) - return xdp_do_redirect_map(dev, xdp, xdp_prog, map); + return xdp_do_redirect_map(dev, xdp, xdp_prog, map, ri); - fwd = dev_get_by_index_rcu(dev_net(dev), index); - ri->ifindex = 0; - if (unlikely(!fwd)) { - err = -EINVAL; - goto err; - } - - err = __bpf_tx_xdp(fwd, NULL, xdp, 0); - if (unlikely(err)) - goto err; - - _trace_xdp_redirect(dev, xdp_prog, index); - return 0; -err: - _trace_xdp_redirect_err(dev, xdp_prog, index, err); - return err; + return xdp_do_redirect_slow(dev, xdp, xdp_prog, ri); } EXPORT_SYMBOL_GPL(xdp_do_redirect);