Commit 0d25c43a authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Daniel Borkmann

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: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarToke Høiland-Jørgensen <toke@toke.dk>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent a7f7547f
...@@ -4,6 +4,8 @@ ...@@ -4,6 +4,8 @@
* Example howto extract XDP RX-queue info * Example howto extract XDP RX-queue info
*/ */
#include <uapi/linux/bpf.h> #include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/in.h>
#include "bpf_helpers.h" #include "bpf_helpers.h"
/* Config setup from with userspace /* Config setup from with userspace
...@@ -14,6 +16,11 @@ ...@@ -14,6 +16,11 @@
struct config { struct config {
__u32 action; __u32 action;
int ifindex; int ifindex;
__u32 options;
};
enum cfg_options_flags {
NO_TOUCH = 0x0U,
READ_MEM = 0x1U,
}; };
struct bpf_map_def SEC("maps") config_map = { struct bpf_map_def SEC("maps") config_map = {
.type = BPF_MAP_TYPE_ARRAY, .type = BPF_MAP_TYPE_ARRAY,
...@@ -90,6 +97,18 @@ int xdp_prognum0(struct xdp_md *ctx) ...@@ -90,6 +97,18 @@ int xdp_prognum0(struct xdp_md *ctx)
if (key == MAX_RXQs) if (key == MAX_RXQs)
rxq_rec->issue++; 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; return config->action;
} }
......
...@@ -50,6 +50,7 @@ static const struct option long_options[] = { ...@@ -50,6 +50,7 @@ static const struct option long_options[] = {
{"sec", required_argument, NULL, 's' }, {"sec", required_argument, NULL, 's' },
{"no-separators", no_argument, NULL, 'z' }, {"no-separators", no_argument, NULL, 'z' },
{"action", required_argument, NULL, 'a' }, {"action", required_argument, NULL, 'a' },
{"readmem", no_argument, NULL, 'r' },
{0, 0, NULL, 0 } {0, 0, NULL, 0 }
}; };
...@@ -66,6 +67,11 @@ static void int_exit(int sig) ...@@ -66,6 +67,11 @@ static void int_exit(int sig)
struct config { struct config {
__u32 action; __u32 action;
int ifindex; int ifindex;
__u32 options;
};
enum cfg_options_flags {
NO_TOUCH = 0x0U,
READ_MEM = 0x1U,
}; };
#define XDP_ACTION_MAX (XDP_TX + 1) #define XDP_ACTION_MAX (XDP_TX + 1)
#define XDP_ACTION_MAX_STRLEN 11 #define XDP_ACTION_MAX_STRLEN 11
...@@ -109,6 +115,16 @@ static void list_xdp_actions(void) ...@@ -109,6 +115,16 @@ static void list_xdp_actions(void)
printf("\n"); printf("\n");
} }
static char* options2str(enum cfg_options_flags flag)
{
if (flag == NO_TOUCH)
return "no_touch";
if (flag & READ_MEM)
return "read";
fprintf(stderr, "ERR: Unknown config option flags");
exit(EXIT_FAIL);
}
static void usage(char *argv[]) static void usage(char *argv[])
{ {
int i; int i;
...@@ -305,7 +321,7 @@ static __u64 calc_errs_pps(struct datarec *r, ...@@ -305,7 +321,7 @@ static __u64 calc_errs_pps(struct datarec *r,
static void stats_print(struct stats_record *stats_rec, static void stats_print(struct stats_record *stats_rec,
struct stats_record *stats_prev, struct stats_record *stats_prev,
int action) int action, __u32 cfg_opt)
{ {
unsigned int nr_rxqs = bpf_map__def(rx_queue_index_map)->max_entries; unsigned int nr_rxqs = bpf_map__def(rx_queue_index_map)->max_entries;
unsigned int nr_cpus = bpf_num_possible_cpus(); unsigned int nr_cpus = bpf_num_possible_cpus();
...@@ -316,8 +332,8 @@ static void stats_print(struct stats_record *stats_rec, ...@@ -316,8 +332,8 @@ static void stats_print(struct stats_record *stats_rec,
int i; int i;
/* Header */ /* Header */
printf("\nRunning XDP on dev:%s (ifindex:%d) action:%s\n", printf("\nRunning XDP on dev:%s (ifindex:%d) action:%s options:%s\n",
ifname, ifindex, action2str(action)); ifname, ifindex, action2str(action), options2str(cfg_opt));
/* stats_global_map */ /* stats_global_map */
{ {
...@@ -399,7 +415,7 @@ static inline void swap(struct stats_record **a, struct stats_record **b) ...@@ -399,7 +415,7 @@ static inline void swap(struct stats_record **a, struct stats_record **b)
*b = tmp; *b = tmp;
} }
static void stats_poll(int interval, int action) static void stats_poll(int interval, int action, __u32 cfg_opt)
{ {
struct stats_record *record, *prev; struct stats_record *record, *prev;
...@@ -410,7 +426,7 @@ static void stats_poll(int interval, int action) ...@@ -410,7 +426,7 @@ static void stats_poll(int interval, int action)
while (1) { while (1) {
swap(&prev, &record); swap(&prev, &record);
stats_collect(record); stats_collect(record);
stats_print(record, prev, action); stats_print(record, prev, action, cfg_opt);
sleep(interval); sleep(interval);
} }
...@@ -421,6 +437,7 @@ static void stats_poll(int interval, int action) ...@@ -421,6 +437,7 @@ static void stats_poll(int interval, int action)
int main(int argc, char **argv) int main(int argc, char **argv)
{ {
__u32 cfg_options= NO_TOUCH ; /* Default: Don't touch packet memory */
struct rlimit r = {10 * 1024 * 1024, RLIM_INFINITY}; struct rlimit r = {10 * 1024 * 1024, RLIM_INFINITY};
struct bpf_prog_load_attr prog_load_attr = { struct bpf_prog_load_attr prog_load_attr = {
.prog_type = BPF_PROG_TYPE_XDP, .prog_type = BPF_PROG_TYPE_XDP,
...@@ -435,6 +452,7 @@ int main(int argc, char **argv) ...@@ -435,6 +452,7 @@ int main(int argc, char **argv)
int interval = 2; int interval = 2;
__u32 key = 0; __u32 key = 0;
char action_str_buf[XDP_ACTION_MAX_STRLEN + 1 /* for \0 */] = { 0 }; char action_str_buf[XDP_ACTION_MAX_STRLEN + 1 /* for \0 */] = { 0 };
int action = XDP_PASS; /* Default action */ int action = XDP_PASS; /* Default action */
char *action_str = NULL; char *action_str = NULL;
...@@ -496,6 +514,9 @@ int main(int argc, char **argv) ...@@ -496,6 +514,9 @@ int main(int argc, char **argv)
action_str = (char *)&action_str_buf; action_str = (char *)&action_str_buf;
strncpy(action_str, optarg, XDP_ACTION_MAX_STRLEN); strncpy(action_str, optarg, XDP_ACTION_MAX_STRLEN);
break; break;
case 'r':
cfg_options |= READ_MEM;
break;
case 'h': case 'h':
error: error:
default: default:
...@@ -522,6 +543,7 @@ int main(int argc, char **argv) ...@@ -522,6 +543,7 @@ int main(int argc, char **argv)
} }
} }
cfg.action = action; cfg.action = action;
cfg.options = cfg_options;
/* Trick to pretty printf with thousands separators use %' */ /* Trick to pretty printf with thousands separators use %' */
if (use_separators) if (use_separators)
...@@ -542,6 +564,6 @@ int main(int argc, char **argv) ...@@ -542,6 +564,6 @@ int main(int argc, char **argv)
return EXIT_FAIL_XDP; return EXIT_FAIL_XDP;
} }
stats_poll(interval, action); stats_poll(interval, action, cfg_options);
return EXIT_OK; return EXIT_OK;
} }
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