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#include <asm/cputable.h>
13
14#include "event.h"
15#include "utils.h"
16#include "lib.h"
17
18extern void thirty_two_instruction_loop_with_ll_sc(u64 loops, u64 *ll_sc_target);
19
20static void setup_event(struct event *e, u64 config, int type, char *name)
21{
22 event_init_opts(e, config, type, name);
23
24 e->attr.disabled = 1;
25 e->attr.exclude_kernel = 1;
26 e->attr.exclude_hv = 1;
27 e->attr.exclude_idle = 1;
28}
29
30static int do_count_loop(struct event *events, u64 instructions,
31 u64 overhead, bool report)
32{
33 s64 difference, expected;
34 double percentage;
35 u64 dummy;
36
37 prctl(PR_TASK_PERF_EVENTS_ENABLE);
38
39 /* Run for 1M instructions */
40 thirty_two_instruction_loop_with_ll_sc(instructions >> 5, &dummy);
41
42 prctl(PR_TASK_PERF_EVENTS_DISABLE);
43
44 event_read(&events[0]);
45 event_read(&events[1]);
46 event_read(&events[2]);
47
48 expected = instructions + overhead + (events[2].result.value * 10);
49 difference = events[0].result.value - expected;
50 percentage = (double)difference / events[0].result.value * 100;
51
52 if (report) {
53 printf("-----\n");
54 event_report(&events[0]);
55 event_report(&events[1]);
56 event_report(&events[2]);
57
58 printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);
59 printf("Expected %llu\n", expected);
60 printf("Actual %llu\n", events[0].result.value);
61 printf("Delta %lld, %f%%\n", difference, percentage);
62 }
63
64 event_reset(&events[0]);
65 event_reset(&events[1]);
66 event_reset(&events[2]);
67
68 if (difference < 0)
69 difference = -difference;
70
71 /* Tolerate a difference below 0.0001 % */
72 difference *= 10000 * 100;
73 if (difference / events[0].result.value)
74 return -1;
75
76 return 0;
77}
78
79/* Count how many instructions it takes to do a null loop */
80static u64 determine_overhead(struct event *events)
81{
82 u64 current, overhead;
83 int i;
84
85 do_count_loop(events, 0, 0, false);
86 overhead = events[0].result.value;
87
88 for (i = 0; i < 100; i++) {
89 do_count_loop(events, 0, 0, false);
90 current = events[0].result.value;
91 if (current < overhead) {
92 printf("Replacing overhead %llu with %llu\n", overhead, current);
93 overhead = current;
94 }
95 }
96
97 return overhead;
98}
99
100#define PM_MRK_STCX_FAIL 0x03e158
101#define PM_STCX_FAIL 0x01e058
102
103static int test_body(void)
104{
105 struct event events[3];
106 u64 overhead;
107
108 // The STCX_FAIL event we use works on Power8 or later
109 SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_2_07));
110
111 setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, PERF_TYPE_HARDWARE, "instructions");
112 setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, PERF_TYPE_HARDWARE, "cycles");
113 setup_event(&events[2], PM_STCX_FAIL, PERF_TYPE_RAW, "stcx_fail");
114
115 if (event_open(&events[0])) {
116 perror("perf_event_open");
117 return -1;
118 }
119
120 if (event_open_with_group(&events[1], events[0].fd)) {
121 perror("perf_event_open");
122 return -1;
123 }
124
125 if (event_open_with_group(&events[2], events[0].fd)) {
126 perror("perf_event_open");
127 return -1;
128 }
129
130 overhead = determine_overhead(events);
131 printf("Overhead of null loop: %llu instructions\n", overhead);
132
133 /* Run for 1Mi instructions */
134 FAIL_IF(do_count_loop(events, 1000000, overhead, true));
135
136 /* Run for 10Mi instructions */
137 FAIL_IF(do_count_loop(events, 10000000, overhead, true));
138
139 /* Run for 100Mi instructions */
140 FAIL_IF(do_count_loop(events, 100000000, overhead, true));
141
142 /* Run for 1Bi instructions */
143 FAIL_IF(do_count_loop(events, 1000000000, overhead, true));
144
145 /* Run for 16Bi instructions */
146 FAIL_IF(do_count_loop(events, 16000000000, overhead, true));
147
148 /* Run for 64Bi instructions */
149 FAIL_IF(do_count_loop(events, 64000000000, overhead, true));
150
151 event_close(&events[0]);
152 event_close(&events[1]);
153
154 return 0;
155}
156
157static int count_ll_sc(void)
158{
159 return eat_cpu(test_body);
160}
161
162int main(void)
163{
164 return test_harness(count_ll_sc, "count_ll_sc");
165}