tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Copyright 2013, Michael Ellerman, IBM Corp.
3 * Licensed under GPLv2.
4 */
5
6#define _GNU_SOURCE
7
8#include <stdio.h>
9#include <stdbool.h>
10#include <string.h>
11#include <sys/prctl.h>
12
13#include "event.h"
14#include "utils.h"
15#include "lib.h"
16
17extern void thirty_two_instruction_loop_with_ll_sc(u64 loops, u64 *ll_sc_target);
18
19static void setup_event(struct event *e, u64 config, int type, char *name)
20{
21 event_init_opts(e, config, type, name);
22
23 e->attr.disabled = 1;
24 e->attr.exclude_kernel = 1;
25 e->attr.exclude_hv = 1;
26 e->attr.exclude_idle = 1;
27}
28
29static int do_count_loop(struct event *events, u64 instructions,
30 u64 overhead, bool report)
31{
32 s64 difference, expected;
33 double percentage;
34 u64 dummy;
35
36 prctl(PR_TASK_PERF_EVENTS_ENABLE);
37
38 /* Run for 1M instructions */
39 thirty_two_instruction_loop_with_ll_sc(instructions >> 5, &dummy);
40
41 prctl(PR_TASK_PERF_EVENTS_DISABLE);
42
43 event_read(&events[0]);
44 event_read(&events[1]);
45 event_read(&events[2]);
46
47 expected = instructions + overhead + (events[2].result.value * 10);
48 difference = events[0].result.value - expected;
49 percentage = (double)difference / events[0].result.value * 100;
50
51 if (report) {
52 printf("-----\n");
53 event_report(&events[0]);
54 event_report(&events[1]);
55 event_report(&events[2]);
56
57 printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);
58 printf("Expected %llu\n", expected);
59 printf("Actual %llu\n", events[0].result.value);
60 printf("Delta %lld, %f%%\n", difference, percentage);
61 }
62
63 event_reset(&events[0]);
64 event_reset(&events[1]);
65 event_reset(&events[2]);
66
67 if (difference < 0)
68 difference = -difference;
69
70 /* Tolerate a difference below 0.0001 % */
71 difference *= 10000 * 100;
72 if (difference / events[0].result.value)
73 return -1;
74
75 return 0;
76}
77
78/* Count how many instructions it takes to do a null loop */
79static u64 determine_overhead(struct event *events)
80{
81 u64 current, overhead;
82 int i;
83
84 do_count_loop(events, 0, 0, false);
85 overhead = events[0].result.value;
86
87 for (i = 0; i < 100; i++) {
88 do_count_loop(events, 0, 0, false);
89 current = events[0].result.value;
90 if (current < overhead) {
91 printf("Replacing overhead %llu with %llu\n", overhead, current);
92 overhead = current;
93 }
94 }
95
96 return overhead;
97}
98
99#define PM_MRK_STCX_FAIL 0x03e158
100#define PM_STCX_FAIL 0x01e058
101
102static int test_body(void)
103{
104 struct event events[3];
105 u64 overhead;
106
107 setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, PERF_TYPE_HARDWARE, "instructions");
108 setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, PERF_TYPE_HARDWARE, "cycles");
109 setup_event(&events[2], PM_STCX_FAIL, PERF_TYPE_RAW, "stcx_fail");
110
111 if (event_open(&events[0])) {
112 perror("perf_event_open");
113 return -1;
114 }
115
116 if (event_open_with_group(&events[1], events[0].fd)) {
117 perror("perf_event_open");
118 return -1;
119 }
120
121 if (event_open_with_group(&events[2], events[0].fd)) {
122 perror("perf_event_open");
123 return -1;
124 }
125
126 overhead = determine_overhead(events);
127 printf("Overhead of null loop: %llu instructions\n", overhead);
128
129 /* Run for 1Mi instructions */
130 FAIL_IF(do_count_loop(events, 1000000, overhead, true));
131
132 /* Run for 10Mi instructions */
133 FAIL_IF(do_count_loop(events, 10000000, overhead, true));
134
135 /* Run for 100Mi instructions */
136 FAIL_IF(do_count_loop(events, 100000000, overhead, true));
137
138 /* Run for 1Bi instructions */
139 FAIL_IF(do_count_loop(events, 1000000000, overhead, true));
140
141 /* Run for 16Bi instructions */
142 FAIL_IF(do_count_loop(events, 16000000000, overhead, true));
143
144 /* Run for 64Bi instructions */
145 FAIL_IF(do_count_loop(events, 64000000000, overhead, true));
146
147 event_close(&events[0]);
148 event_close(&events[1]);
149
150 return 0;
151}
152
153static int count_ll_sc(void)
154{
155 return eat_cpu(test_body);
156}
157
158int main(void)
159{
160 return test_harness(count_ll_sc, "count_ll_sc");
161}