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 
17 extern void thirty_two_instruction_loop_with_ll_sc(u64 loops, u64 *ll_sc_target);
18 
setup_event(struct event * e,u64 config,int type,char * name)19 static 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 
do_count_loop(struct event * events,u64 instructions,u64 overhead,bool report)29 static 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 */
determine_overhead(struct event * events)79 static 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 
test_body(void)102 static int test_body(void)
103 {
104 	struct event events[3];
105 	u64 overhead;
106 
107 	// The STCX_FAIL event we use works on Power8 or later
108 	SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_2_07));
109 
110 	setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, PERF_TYPE_HARDWARE, "instructions");
111 	setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, PERF_TYPE_HARDWARE, "cycles");
112 	setup_event(&events[2], PM_STCX_FAIL, PERF_TYPE_RAW, "stcx_fail");
113 
114 	if (event_open(&events[0])) {
115 		perror("perf_event_open");
116 		return -1;
117 	}
118 
119 	if (event_open_with_group(&events[1], events[0].fd)) {
120 		perror("perf_event_open");
121 		return -1;
122 	}
123 
124 	if (event_open_with_group(&events[2], events[0].fd)) {
125 		perror("perf_event_open");
126 		return -1;
127 	}
128 
129 	overhead = determine_overhead(events);
130 	printf("Overhead of null loop: %llu instructions\n", overhead);
131 
132 	/* Run for 1Mi instructions */
133 	FAIL_IF(do_count_loop(events, 1000000, overhead, true));
134 
135 	/* Run for 10Mi instructions */
136 	FAIL_IF(do_count_loop(events, 10000000, overhead, true));
137 
138 	/* Run for 100Mi instructions */
139 	FAIL_IF(do_count_loop(events, 100000000, overhead, true));
140 
141 	/* Run for 1Bi instructions */
142 	FAIL_IF(do_count_loop(events, 1000000000, overhead, true));
143 
144 	/* Run for 16Bi instructions */
145 	FAIL_IF(do_count_loop(events, 16000000000, overhead, true));
146 
147 	/* Run for 64Bi instructions */
148 	FAIL_IF(do_count_loop(events, 64000000000, overhead, true));
149 
150 	event_close(&events[0]);
151 	event_close(&events[1]);
152 
153 	return 0;
154 }
155 
count_ll_sc(void)156 static int count_ll_sc(void)
157 {
158 	return eat_cpu(test_body);
159 }
160 
main(void)161 int main(void)
162 {
163 	return test_harness(count_ll_sc, "count_ll_sc");
164 }
165