136 lines
3 KiB
C
136 lines
3 KiB
C
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/*
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* Copyright 2013, Michael Ellerman, IBM Corp.
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* Licensed under GPLv2.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdbool.h>
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#include <string.h>
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#include <sys/prctl.h>
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#include "event.h"
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#include "utils.h"
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extern void thirty_two_instruction_loop(u64 loops);
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static void setup_event(struct event *e, u64 config, char *name)
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{
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event_init_opts(e, config, PERF_TYPE_HARDWARE, name);
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e->attr.disabled = 1;
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e->attr.exclude_kernel = 1;
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e->attr.exclude_hv = 1;
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e->attr.exclude_idle = 1;
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}
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static int do_count_loop(struct event *events, u64 instructions,
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u64 overhead, bool report)
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{
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s64 difference, expected;
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double percentage;
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prctl(PR_TASK_PERF_EVENTS_ENABLE);
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/* Run for 1M instructions */
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thirty_two_instruction_loop(instructions >> 5);
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prctl(PR_TASK_PERF_EVENTS_DISABLE);
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event_read(&events[0]);
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event_read(&events[1]);
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expected = instructions + overhead;
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difference = events[0].result.value - expected;
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percentage = (double)difference / events[0].result.value * 100;
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if (report) {
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event_report(&events[0]);
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event_report(&events[1]);
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printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);
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printf("Expected %llu\n", expected);
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printf("Actual %llu\n", events[0].result.value);
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printf("Delta %lld, %f%%\n", difference, percentage);
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}
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event_reset(&events[0]);
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event_reset(&events[1]);
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if (difference < 0)
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difference = -difference;
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/* Tolerate a difference below 0.0001 % */
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difference *= 10000 * 100;
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if (difference / events[0].result.value)
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return -1;
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return 0;
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}
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/* Count how many instructions it takes to do a null loop */
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static u64 determine_overhead(struct event *events)
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{
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u64 current, overhead;
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int i;
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do_count_loop(events, 0, 0, false);
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overhead = events[0].result.value;
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for (i = 0; i < 100; i++) {
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do_count_loop(events, 0, 0, false);
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current = events[0].result.value;
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if (current < overhead) {
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printf("Replacing overhead %llu with %llu\n", overhead, current);
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overhead = current;
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}
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}
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return overhead;
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}
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static int count_instructions(void)
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{
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struct event events[2];
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u64 overhead;
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setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, "instructions");
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setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, "cycles");
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if (event_open(&events[0])) {
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perror("perf_event_open");
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return -1;
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}
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if (event_open_with_group(&events[1], events[0].fd)) {
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perror("perf_event_open");
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return -1;
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}
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overhead = determine_overhead(events);
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printf("Overhead of null loop: %llu instructions\n", overhead);
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/* Run for 1M instructions */
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FAIL_IF(do_count_loop(events, 0x100000, overhead, true));
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/* Run for 10M instructions */
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FAIL_IF(do_count_loop(events, 0xa00000, overhead, true));
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/* Run for 100M instructions */
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FAIL_IF(do_count_loop(events, 0x6400000, overhead, true));
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/* Run for 1G instructions */
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FAIL_IF(do_count_loop(events, 0x40000000, overhead, true));
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event_close(&events[0]);
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event_close(&events[1]);
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return 0;
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}
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int main(void)
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{
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return test_harness(count_instructions, "count_instructions");
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}
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