samples/bpf: xdpsock: Add sched policy and priority support

By default, TX schedule policy is SCHED_OTHER (round-robin time-sharing).
To improve TX cyclic scheduling, we add SCHED_FIFO policy and its priority
by using -W FIFO or --policy=FIFO and -U <PRIO> or --schpri=<PRIO>.

A) From xdpsock --app-stats, for SCHED_OTHER policy:
   $ xdpsock -i eth0 -t -N -z -T 1000 -b 16 -C 100000 -a

                      period     min        ave        max        cycle
   Cyclic TX          1000000    53507      75334      712642     6250

B) For SCHED_FIFO policy and schpri=50:
   $ xdpsock -i eth0 -t -N -z -T 1000 -b 16 -C 100000 -a -W FIFO -U 50

                      period     min        ave        max        cycle
   Cyclic TX          1000000    3699       24859      54397      6250

Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211230035447.523177-6-boon.leong.ong@intel.com

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index a2a42ec..b7d0f53 100644 (file)
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -31,6 +31,7 @@
 #include <sys/un.h>
 #include <time.h>
 #include <unistd.h>
+#include <sched.h>
 
 #include <bpf/libbpf.h>
 #include <bpf/xsk.h>
@@ -66,6 +67,8 @@
 #define NSEC_PER_SEC           1000000000UL
 #define NSEC_PER_USEC          1000
 
+#define SCHED_PRI__DEFAULT     0
+
 typedef __u64 u64;
 typedef __u32 u32;
 typedef __u16 u16;
@@ -123,6 +126,8 @@ static bool opt_busy_poll;
 static bool opt_reduced_cap;
 static clockid_t opt_clock = CLOCK_MONOTONIC;
 static unsigned long opt_tx_cycle_ns;
+static int opt_schpolicy = SCHED_OTHER;
+static int opt_schprio = SCHED_PRI__DEFAULT;
 
 struct vlan_ethhdr {
        unsigned char h_dest[6];
@@ -198,6 +203,15 @@ static const struct clockid_map {
        { NULL }
 };
 
+static const struct sched_map {
+       const char *name;
+       int policy;
+} schmap[] = {
+       { "OTHER", SCHED_OTHER },
+       { "FIFO", SCHED_FIFO },
+       { NULL }
+};
+
 static int num_socks;
 struct xsk_socket_info *xsks[MAX_SOCKS];
 int sock;
@@ -216,6 +230,20 @@ static int get_clockid(clockid_t *id, const char *name)
        return -1;
 }
 
+static int get_schpolicy(int *policy, const char *name)
+{
+       const struct sched_map *sch;
+
+       for (sch = schmap; sch->name; sch++) {
+               if (strcasecmp(sch->name, name) == 0) {
+                       *policy = sch->policy;
+                       return 0;
+               }
+       }
+
+       return -1;
+}
+
 static unsigned long get_nsecs(void)
 {
        struct timespec ts;
@@ -1019,6 +1047,8 @@ static struct option long_options[] = {
        {"tx-dmac", required_argument, 0, 'G'},
        {"tx-smac", required_argument, 0, 'H'},
        {"tx-cycle", required_argument, 0, 'T'},
+       {"policy", required_argument, 0, 'W'},
+       {"schpri", required_argument, 0, 'U'},
        {"extra-stats", no_argument, 0, 'x'},
        {"quiet", no_argument, 0, 'Q'},
        {"app-stats", no_argument, 0, 'a'},
@@ -1066,6 +1096,8 @@ static void usage(const char *prog)
                "  -G, --tx-dmac=<MAC>  Dest MAC addr of TX frame in aa:bb:cc:dd:ee:ff format (For -V|--tx-vlan)\n"
                "  -H, --tx-smac=<MAC>  Src MAC addr of TX frame in aa:bb:cc:dd:ee:ff format (For -V|--tx-vlan)\n"
                "  -T, --tx-cycle=n     Tx cycle time in micro-seconds (For -t|--txonly).\n"
+               "  -W, --policy=POLICY  Schedule policy. Default: SCHED_OTHER\n"
+               "  -U, --schpri=n       Schedule priority. Default: %d\n"
                "  -x, --extra-stats    Display extra statistics.\n"
                "  -Q, --quiet          Do not display any stats.\n"
                "  -a, --app-stats      Display application (syscall) statistics.\n"
@@ -1076,7 +1108,8 @@ static void usage(const char *prog)
        fprintf(stderr, str, prog, XSK_UMEM__DEFAULT_FRAME_SIZE,
                opt_batch_size, MIN_PKT_SIZE, MIN_PKT_SIZE,
                XSK_UMEM__DEFAULT_FRAME_SIZE, opt_pkt_fill_pattern,
-               VLAN_VID__DEFAULT, VLAN_PRI__DEFAULT);
+               VLAN_VID__DEFAULT, VLAN_PRI__DEFAULT,
+               SCHED_PRI__DEFAULT);
 
        exit(EXIT_FAILURE);
 }
@@ -1088,7 +1121,8 @@ static void parse_command_line(int argc, char **argv)
        opterr = 0;
 
        for (;;) {
-               c = getopt_long(argc, argv, "Frtli:q:pSNn:w:czf:muMd:b:C:s:P:VJ:K:G:H:T:xQaI:BR",
+               c = getopt_long(argc, argv,
+                               "Frtli:q:pSNn:w:czf:muMd:b:C:s:P:VJ:K:G:H:T:W:U:xQaI:BR",
                                long_options, &option_index);
                if (c == -1)
                        break;
@@ -1206,6 +1240,17 @@ static void parse_command_line(int argc, char **argv)
                        opt_tx_cycle_ns = atoi(optarg);
                        opt_tx_cycle_ns *= NSEC_PER_USEC;
                        break;
+               case 'W':
+                       if (get_schpolicy(&opt_schpolicy, optarg)) {
+                               fprintf(stderr,
+                                       "ERROR: Invalid policy %s. Default to SCHED_OTHER.\n",
+                                       optarg);
+                               opt_schpolicy = SCHED_OTHER;
+                       }
+                       break;
+               case 'U':
+                       opt_schprio = atoi(optarg);
+                       break;
                case 'x':
                        opt_extra_stats = 1;
                        break;
@@ -1780,6 +1825,7 @@ int main(int argc, char **argv)
        struct __user_cap_data_struct data[2] = { { 0 } };
        struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
        bool rx = false, tx = false;
+       struct sched_param schparam;
        struct xsk_umem_info *umem;
        struct bpf_object *obj;
        int xsks_map_fd = 0;
@@ -1881,6 +1927,16 @@ int main(int argc, char **argv)
        prev_time = get_nsecs();
        start_time = prev_time;
 
+       /* Configure sched priority for better wake-up accuracy */
+       memset(&schparam, 0, sizeof(schparam));
+       schparam.sched_priority = opt_schprio;
+       ret = sched_setscheduler(0, opt_schpolicy, &schparam);
+       if (ret) {
+               fprintf(stderr, "Error(%d) in setting priority(%d): %s\n",
+                       errno, opt_schprio, strerror(errno));
+               goto out;
+       }
+
        if (opt_bench == BENCH_RXDROP)
                rx_drop_all();
        else if (opt_bench == BENCH_TXONLY)
@@ -1888,6 +1944,7 @@ int main(int argc, char **argv)
        else
                l2fwd_all();
 
+out:
        benchmark_done = true;
 
        if (!opt_quiet)