mirror of
https://git.postgresql.org/git/postgresql.git
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185 lines
3.7 KiB
C
185 lines
3.7 KiB
C
/*
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* pg_test_timing.c
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* tests overhead of timing calls and their monotonicity: that
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* they always move forward
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*/
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#include "postgres_fe.h"
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#include "getopt_long.h"
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#include "portability/instr_time.h"
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static const char *progname;
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static int32 test_duration = 3;
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static void handle_args(int argc, char *argv[]);
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static uint64 test_timing(int32);
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static void output(uint64 loop_count);
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/* record duration in powers of 2 microseconds */
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int64 histogram[32];
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int
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main(int argc, char *argv[])
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{
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uint64 loop_count;
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progname = get_progname(argv[0]);
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handle_args(argc, argv);
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loop_count = test_timing(test_duration);
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output(loop_count);
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return 0;
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}
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static void
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handle_args(int argc, char *argv[])
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{
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static struct option long_options[] = {
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{"duration", required_argument, NULL, 'd'},
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{NULL, 0, NULL, 0}
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};
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int option; /* Command line option */
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int optindex = 0; /* used by getopt_long */
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if (argc > 1)
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{
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if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0 ||
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strcmp(argv[1], "-?") == 0)
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{
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printf("Usage: %s [-d DURATION]\n", progname);
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exit(0);
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}
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if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
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{
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puts("pg_test_timing (PostgreSQL) " PG_VERSION);
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exit(0);
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}
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}
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while ((option = getopt_long(argc, argv, "d:",
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long_options, &optindex)) != -1)
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{
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switch (option)
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{
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case 'd':
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test_duration = atoi(optarg);
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break;
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default:
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fprintf(stderr, "Try \"%s --help\" for more information.\n",
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progname);
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exit(1);
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break;
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}
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}
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if (argc > optind)
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{
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fprintf(stderr,
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"%s: too many command-line arguments (first is \"%s\")\n",
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progname, argv[optind]);
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fprintf(stderr, "Try \"%s --help\" for more information.\n",
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progname);
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exit(1);
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}
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if (test_duration > 0)
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{
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printf("Testing timing overhead for %d seconds.\n", test_duration);
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}
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else
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{
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fprintf(stderr,
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"%s: duration must be a positive integer (duration is \"%d\")\n",
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progname, test_duration);
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fprintf(stderr, "Try \"%s --help\" for more information.\n",
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progname);
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exit(1);
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}
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}
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static uint64
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test_timing(int32 duration)
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{
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uint64 total_time;
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int64 time_elapsed = 0;
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uint64 loop_count = 0;
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uint64 prev, cur;
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instr_time start_time, end_time, temp;
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total_time = duration > 0 ? duration * 1000000 : 0;
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INSTR_TIME_SET_CURRENT(start_time);
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cur = INSTR_TIME_GET_MICROSEC(start_time);
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while (time_elapsed < total_time)
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{
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int32 diff, bits = 0;
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prev = cur;
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INSTR_TIME_SET_CURRENT(temp);
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cur = INSTR_TIME_GET_MICROSEC(temp);
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diff = cur - prev;
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/* Did time go backwards? */
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if (diff < 0)
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{
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printf("Detected clock going backwards in time.\n");
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printf("Time warp: %d microseconds\n", diff);
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exit(1);
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}
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/* What is the highest bit in the time diff? */
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while (diff)
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{
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diff >>= 1;
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bits++;
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}
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/* Update appropriate duration bucket */
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histogram[bits]++;
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loop_count++;
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INSTR_TIME_SUBTRACT(temp, start_time);
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time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
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}
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INSTR_TIME_SET_CURRENT(end_time);
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INSTR_TIME_SUBTRACT(end_time, start_time);
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printf("Per loop time including overhead: %0.2f nsec\n",
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INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
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return loop_count;
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}
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static void
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output(uint64 loop_count)
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{
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int64 max_bit = 31, i;
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/* find highest bit value */
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while (max_bit > 0 && histogram[max_bit] == 0)
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max_bit--;
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printf("Histogram of timing durations:\n");
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printf("%6s %10s %10s\n", "< usec", "% of total", "count");
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for (i = 0; i <= max_bit; i++)
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{
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char buf[100];
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/* lame hack to work around INT64_FORMAT deficiencies */
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snprintf(buf, sizeof(buf), INT64_FORMAT, histogram[i]);
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printf("%6ld %9.5f %10s\n", 1l << i,
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(double) histogram[i] * 100 / loop_count, buf);
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}
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}
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