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| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2018-06-25 17:27:43 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-06-29 00:50:20 +0300 |
| commit | 0d25c43ab988766ad52ff2930af3bf47d92c20ac (patch) | |
| tree | c3185ab7937c51a3a13043bd9263bec4957dc3f1 /samples/bpf/xdp_rxq_info_kern.c | |
| parent | a7f7547f5e2b90554b0f3d1604899a4f26dba92d (diff) | |
| download | linux-0d25c43ab988766ad52ff2930af3bf47d92c20ac.tar.xz | |
samples/bpf: extend xdp_rxq_info to read packet payload
There is a cost associated with reading the packet data payload
that this test ignored. Add option --read to allow enabling
reading part of the payload.
This sample/tool helps us analyse an issue observed with a NIC
mlx5 (ConnectX-5 Ex) and an Intel(R) Xeon(R) CPU E5-1650 v4.
With no_touch of data:
Running XDP on dev:mlx5p1 (ifindex:8) action:XDP_DROP options:no_touch
XDP stats CPU pps issue-pps
XDP-RX CPU 0 14,465,157 0
XDP-RX CPU 1 14,464,728 0
XDP-RX CPU 2 14,465,283 0
XDP-RX CPU 3 14,465,282 0
XDP-RX CPU 4 14,464,159 0
XDP-RX CPU 5 14,465,379 0
XDP-RX CPU total 86,789,992
When not touching data, we observe that the CPUs have idle cycles.
When reading data the CPUs are 100% busy in softirq.
With reading data:
Running XDP on dev:mlx5p1 (ifindex:8) action:XDP_DROP options:read
XDP stats CPU pps issue-pps
XDP-RX CPU 0 9,620,639 0
XDP-RX CPU 1 9,489,843 0
XDP-RX CPU 2 9,407,854 0
XDP-RX CPU 3 9,422,289 0
XDP-RX CPU 4 9,321,959 0
XDP-RX CPU 5 9,395,242 0
XDP-RX CPU total 56,657,828
The effect seen above is a result of cache-misses occuring when
more RXQs are being used. Based on perf-event observations, our
conclusion is that the CPUs DDIO (Direct Data I/O) choose to
deliver packet into main memory, instead of L3-cache. We also
found, that this can be mitigated by either using less RXQs or by
reducing NICs the RX-ring size.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'samples/bpf/xdp_rxq_info_kern.c')
| -rw-r--r-- | samples/bpf/xdp_rxq_info_kern.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/samples/bpf/xdp_rxq_info_kern.c b/samples/bpf/xdp_rxq_info_kern.c index 3fd209291653..61af6210df2f 100644 --- a/samples/bpf/xdp_rxq_info_kern.c +++ b/samples/bpf/xdp_rxq_info_kern.c @@ -4,6 +4,8 @@ * Example howto extract XDP RX-queue info */ #include <uapi/linux/bpf.h> +#include <uapi/linux/if_ether.h> +#include <uapi/linux/in.h> #include "bpf_helpers.h" /* Config setup from with userspace @@ -14,6 +16,11 @@ struct config { __u32 action; int ifindex; + __u32 options; +}; +enum cfg_options_flags { + NO_TOUCH = 0x0U, + READ_MEM = 0x1U, }; struct bpf_map_def SEC("maps") config_map = { .type = BPF_MAP_TYPE_ARRAY, @@ -90,6 +97,18 @@ int xdp_prognum0(struct xdp_md *ctx) if (key == MAX_RXQs) rxq_rec->issue++; + /* Default: Don't touch packet data, only count packets */ + if (unlikely(config->options & READ_MEM)) { + struct ethhdr *eth = data; + + if (eth + 1 > data_end) + return XDP_ABORTED; + + /* Avoid compiler removing this: Drop non 802.3 Ethertypes */ + if (ntohs(eth->h_proto) < ETH_P_802_3_MIN) + return XDP_ABORTED; + } + return config->action; } |