util/xdp_sample: Calculate average PPS from elapsed time

Instead of counting the number of rounds in the polling loop, actually
calculate the total runtime in seconds and compute the average PPS from
that. Also print the duration as part of the end-of-run statistics.

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>

Author: tohojo

lib/util/xdp_sample.c

@@ -154,6 +154,7 @@ size_t sample_map_count[NUM_MAP];
 enum log_level sample_log_level;
 struct sample_output sample_out;
 unsigned long sample_interval;
+__u64 sample_start_time;
 bool sample_err_exp;
 int sample_xdp_cnt;
 int sample_n_cpus;
@@ -1339,23 +1340,26 @@ int __sample_init(int mask, int ifindex_from, int ifindex_to)
 
 static void sample_summary_print(void)
 {
-	double num = sample_out.rx_cnt.num;
+	__u64 start = sample_start_time;
+	__u64 now = gettime();
+	double dur_s = ((double)now - start) / NANOSEC_PER_SEC;
 
+	print_always("  Duration            : %.1fs\n", dur_s);
 	if (sample_out.totals.rx) {
 		double pkts = sample_out.totals.rx;
 
 		print_always("  Packets received    : %'-10" PRIu64 "\n",
 			     (uint64_t)sample_out.totals.rx);
 		print_always("  Average packets/s   : %'-10.0f\n",
-			     round(pkts / num));
+			     round(pkts / dur_s));
 	}
 	if (sample_out.totals.redir) {
 		double pkts = sample_out.totals.redir;
 
 		print_always("  Packets redirected  : %'-10" PRIu64 "\n",
 			     sample_out.totals.redir);
 		print_always("  Average redir/s     : %'-10.0f\n",
-			     round(pkts / num));
+			     round(pkts / dur_s));
 	}
 	if (sample_out.totals.drop)
 		print_always("  Rx dropped          : %'-10" PRIu64 "\n",
@@ -1372,7 +1376,7 @@ static void sample_summary_print(void)
 		print_always("  Packets transmitted : %'-10" PRIu64 "\n",
 			     sample_out.totals.xmit);
 		print_always("  Average transmit/s  : %'-10.0f\n",
-			     round(pkts / num));
+			     round(pkts / dur_s));
 	}
 }
 
@@ -1439,7 +1443,6 @@ static void sample_summary_update(struct sample_output *out)
 	sample_out.totals.drop_xmit += out->totals.drop_xmit;
 	sample_out.totals.err += out->totals.err;
 	sample_out.totals.xmit += out->totals.xmit;
-	sample_out.rx_cnt.num++;
 }
 
 static void sample_stats_print(int mask, struct stats_record *cur,
@@ -1585,6 +1588,8 @@ int sample_run(unsigned int interval, void (*post_cb)(void *), void *ctx)
 	if (!prev)
 		goto end_rec;
 
+	sample_start_time = gettime();
+
 	ret = sample_stats_collect(rec);
 	if (ret < 0)
 		goto end_rec_prev;