bench: print clock info

Author: Raimo33

src/bench.c

@@ -254,6 +254,7 @@ int main(int argc, char** argv) {
     data.pubkeylen = 33;
     CHECK(secp256k1_ec_pubkey_serialize(data.ctx, data.pubkey, &data.pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED) == 1);
 
+    print_clock_info();
     print_output_table_header_row();
     if (d || have_flag(argc, argv, "ecdsa") || have_flag(argc, argv, "verify") || have_flag(argc, argv, "ecdsa_verify")) run_benchmark("ecdsa_verify", bench_verify, NULL, NULL, &data, 10, iters);
 

src/bench.h

@@ -202,6 +202,14 @@ static int get_iters(int default_iters) {
     }
 }
 
+static void print_clock_info(void) {
+#if defined(CLOCK_PROCESS_CPUTIME_ID)
+    printf("INFO: Using per-process CPU timer\n\n");
+#else
+    printf("WARN: using Wall-clock timer, results can be strongly influenced by other running processes\n\n");
+#endif
+}
+
 static void print_output_table_header_row(void) {
     char* bench_str = "Benchmark";     /* left justified */
     char* min_str = "    Min(us)    "; /* center alignment */

src/bench_ecmult.c

@@ -365,6 +365,7 @@ int main(int argc, char **argv) {
     }
     secp256k1_ge_set_all_gej_var(data.pubkeys, data.pubkeys_gej, POINTS);
 
+    print_clock_info();
     print_output_table_header_row();
     /* Initialize offset1 and offset2 */
     hash_into_offset(&data, 0);

src/bench_internal.c

@@ -401,6 +401,7 @@ int main(int argc, char **argv) {
         }
     }
 
+    print_clock_info();
     print_output_table_header_row();
 
     if (d || have_flag(argc, argv, "scalar") || have_flag(argc, argv, "half")) run_benchmark("scalar_half", bench_scalar_half, bench_setup, NULL, &data, 10, iters*100);