1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include <vespa/vespalib/util/spin_lock.h>
#include <vespa/vespalib/util/atomic.h>
#include <vespa/vespalib/util/benchmark_timer.h>
#include <vespa/vespalib/util/time.h>
#include <vespa/vespalib/testkit/test_kit.h>
#include <array>
using namespace vespalib;
using namespace vespalib::atomic;
bool verbose = false;
double budget = 0.25;
size_t thread_safety_work = 1000000;
struct DummyLock {
void lock() {}
void unlock() {}
};
//-----------------------------------------------------------------------------
struct MyState {
static constexpr size_t SZ = 5;
std::array<size_t,SZ> state = {0,0,0,0,0};
void update() {
std::array<size_t,SZ> tmp;
for (size_t i = 0; i < SZ; ++i) {
store_ref_relaxed(tmp[i], load_ref_relaxed(state[i]));
}
for (size_t i = 0; i < SZ; ++i) {
store_ref_relaxed(state[i], load_ref_relaxed(tmp[i]) + 1);
}
}
bool check(size_t expect) const {
for (const auto& value: state) {
if (load_ref_relaxed(value) != expect) {
return false;
}
}
return true;
}
void report(size_t expect, const char *name) const {
if (check(expect)) {
fprintf(stderr, "%s is thread safe\n", name);
} else {
fprintf(stderr, "%s is not thread safe\n", name);
fprintf(stderr, " expected %zu, got [%zu,%zu,%zu,%zu,%zu]\n",
expect, state[0], state[1], state[2], state[3], state[4]);
}
}
};
//-----------------------------------------------------------------------------
template <typename T> void basic_usage() {
T lock;
{
std::lock_guard guard(lock);
}
{
std::unique_lock guard(lock);
}
}
//-----------------------------------------------------------------------------
template <typename T> size_t thread_safety_loop(T &lock, MyState &state, size_t thread_id, size_t thread_limit) {
size_t loop_cnt = (thread_safety_work / thread_limit);
TEST_BARRIER();
auto t0 = steady_clock::now();
TEST_BARRIER();
if (thread_id < thread_limit) {
for (size_t i = 0; i < loop_cnt; ++i) {
std::lock_guard guard(lock);
state.update();
}
}
TEST_BARRIER();
auto t1 = steady_clock::now();
if (thread_id == 0) {
auto t2 = steady_clock::now();
size_t total_ms = count_ms(t2 - t0);
fprintf(stderr, "---> thread_safety_loop with %zu threads used %zu ms\n", thread_limit, total_ms);
}
TEST_BARRIER();
if (verbose && (thread_id < thread_limit)) {
size_t local_ms = count_ms(t1 - t0);
fprintf(stderr, " -- thread %zu used %zu ms\n", thread_id, local_ms);
}
TEST_BARRIER();
return (loop_cnt * thread_limit);
}
//-----------------------------------------------------------------------------
template <typename T> void estimate_cost(const char *name) __attribute__((noinline));
template <typename T> void estimate_cost(const char *name) {
T lock;
auto lock_loop = [&]()
{
// 250 * 4 = 1000 times lock/unlock
for (size_t i = 0; i < 250; ++i) {
// 4 times lock/unlock
lock.lock();
lock.unlock();
lock.lock();
lock.unlock();
lock.lock();
lock.unlock();
lock.lock();
lock.unlock();
}
};
BenchmarkTimer timer(budget);
while (timer.has_budget()) {
timer.before();
lock_loop();
timer.after();
}
auto cost_ns = timer.min_time() * 1000.0 * 1000.0;
fprintf(stderr, "%s: estimated lock/unlock time: %g ns\n", name, cost_ns);
}
//-----------------------------------------------------------------------------
TEST("require that locks can be used with lock_guard and unique_lock") {
TEST_DO(basic_usage<DummyLock>());
TEST_DO(basic_usage<SpinLock>());
}
TEST_MT_FF("report whether DummyLock is thread safe", 24, DummyLock(), MyState()) {
size_t expect = thread_safety_loop(f1, f2, thread_id, 24);
if (thread_id == 0) {
f2.report(expect, "DummyLock");
}
}
TEST_MT_FF("require that SpinLock is thread safe", 24, SpinLock(), MyState()) {
size_t expect = thread_safety_loop(f1, f2, thread_id, 24);
expect += thread_safety_loop(f1, f2, thread_id, 12);
expect += thread_safety_loop(f1, f2, thread_id, 6);
expect += thread_safety_loop(f1, f2, thread_id, 3);
if (thread_id == 0) {
f2.report(expect, "SpinLock");
EXPECT_TRUE(f2.check(expect));
}
}
TEST_MT_FF("require that std::mutex is thread safe", 24, std::mutex(), MyState()) {
size_t expect = thread_safety_loop(f1, f2, thread_id, 24);
expect += thread_safety_loop(f1, f2, thread_id, 12);
expect += thread_safety_loop(f1, f2, thread_id, 6);
expect += thread_safety_loop(f1, f2, thread_id, 3);
if (thread_id == 0) {
f2.report(expect, "std::mutex");
EXPECT_TRUE(f2.check(expect));
}
}
TEST("estimate single-threaded lock/unlock cost") {
estimate_cost<DummyLock>("DummyLock");
estimate_cost<SpinLock>("SpinLock");
estimate_cost<std::mutex>("std::mutex");
}
int main(int argc, char **argv) {
TEST_MASTER.init(__FILE__);
if ((argc == 2) && (argv[1] == std::string("verbose"))) {
verbose = true;
budget = 10.0;
thread_safety_work = 32000000;
}
TEST_RUN_ALL();
return (TEST_MASTER.fini() ? 0 : 1);
}
|
