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authorJesper Dangaard Brouer <brouer@redhat.com>2018-06-25 16:27:43 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2018-06-28 23:50:20 +0200
commit0d25c43ab988766ad52ff2930af3bf47d92c20ac (patch)
treec3185ab7937c51a3a13043bd9263bec4957dc3f1 /samples/bpf/xdp_rxq_info_kern.c
parenta7f7547f5e2b90554b0f3d1604899a4f26dba92d (diff)
downloadlinux-stericsson-0d25c43ab988766ad52ff2930af3bf47d92c20ac.tar.gz
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.c19
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;
}