// SPDX-License-Identifier: GPL-2.0-only
|
/*
|
* Copyright 2013, Michael Ellerman, IBM Corp.
|
*/
|
|
#define _GNU_SOURCE
|
|
#include <stdio.h>
|
#include <stdbool.h>
|
#include <string.h>
|
#include <sys/prctl.h>
|
|
#include "event.h"
|
#include "utils.h"
|
#include "lib.h"
|
|
extern void thirty_two_instruction_loop(u64 loops);
|
|
static void setup_event(struct event *e, u64 config, char *name)
|
{
|
event_init_opts(e, config, PERF_TYPE_HARDWARE, name);
|
|
e->attr.disabled = 1;
|
e->attr.exclude_kernel = 1;
|
e->attr.exclude_hv = 1;
|
e->attr.exclude_idle = 1;
|
}
|
|
static int do_count_loop(struct event *events, u64 instructions,
|
u64 overhead, bool report)
|
{
|
s64 difference, expected;
|
double percentage;
|
|
prctl(PR_TASK_PERF_EVENTS_ENABLE);
|
|
/* Run for 1M instructions */
|
thirty_two_instruction_loop(instructions >> 5);
|
|
prctl(PR_TASK_PERF_EVENTS_DISABLE);
|
|
event_read(&events[0]);
|
event_read(&events[1]);
|
|
expected = instructions + overhead;
|
difference = events[0].result.value - expected;
|
percentage = (double)difference / events[0].result.value * 100;
|
|
if (report) {
|
event_report(&events[0]);
|
event_report(&events[1]);
|
|
printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);
|
printf("Expected %llu\n", expected);
|
printf("Actual %llu\n", events[0].result.value);
|
printf("Delta %lld, %f%%\n", difference, percentage);
|
}
|
|
event_reset(&events[0]);
|
event_reset(&events[1]);
|
|
if (difference < 0)
|
difference = -difference;
|
|
/* Tolerate a difference below 0.0001 % */
|
difference *= 10000 * 100;
|
if (difference / events[0].result.value)
|
return -1;
|
|
return 0;
|
}
|
|
/* Count how many instructions it takes to do a null loop */
|
static u64 determine_overhead(struct event *events)
|
{
|
u64 current, overhead;
|
int i;
|
|
do_count_loop(events, 0, 0, false);
|
overhead = events[0].result.value;
|
|
for (i = 0; i < 100; i++) {
|
do_count_loop(events, 0, 0, false);
|
current = events[0].result.value;
|
if (current < overhead) {
|
printf("Replacing overhead %llu with %llu\n", overhead, current);
|
overhead = current;
|
}
|
}
|
|
return overhead;
|
}
|
|
static int test_body(void)
|
{
|
struct event events[2];
|
u64 overhead;
|
|
setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, "instructions");
|
setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, "cycles");
|
|
if (event_open(&events[0])) {
|
perror("perf_event_open");
|
return -1;
|
}
|
|
if (event_open_with_group(&events[1], events[0].fd)) {
|
perror("perf_event_open");
|
return -1;
|
}
|
|
overhead = determine_overhead(events);
|
printf("Overhead of null loop: %llu instructions\n", overhead);
|
|
/* Run for 1Mi instructions */
|
FAIL_IF(do_count_loop(events, 1000000, overhead, true));
|
|
/* Run for 10Mi instructions */
|
FAIL_IF(do_count_loop(events, 10000000, overhead, true));
|
|
/* Run for 100Mi instructions */
|
FAIL_IF(do_count_loop(events, 100000000, overhead, true));
|
|
/* Run for 1Bi instructions */
|
FAIL_IF(do_count_loop(events, 1000000000, overhead, true));
|
|
/* Run for 16Bi instructions */
|
FAIL_IF(do_count_loop(events, 16000000000, overhead, true));
|
|
/* Run for 64Bi instructions */
|
FAIL_IF(do_count_loop(events, 64000000000, overhead, true));
|
|
event_close(&events[0]);
|
event_close(&events[1]);
|
|
return 0;
|
}
|
|
static int count_instructions(void)
|
{
|
return eat_cpu(test_body);
|
}
|
|
int main(void)
|
{
|
return test_harness(count_instructions, "count_instructions");
|
}
|
