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
|
// Copyright 2017 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <sys/param.h>
#include <sys/types.h>
#include <sys/resource.h>
#include <err.h>
#include <unistd.h>
#include <cerrno>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
// Marked as volatile to force the C compiler to calculate it.
volatile uint64_t volatile_counter;
static void WasteUserTime() {
volatile_counter = 0;
while (true) {
volatile_counter++;
if (volatile_counter == 10000000) {
break;
}
}
}
static void WasteSystemTime() {
char current_dir_path[MAXPATHLEN];
if (getcwd(current_dir_path, sizeof(current_dir_path)) == NULL) {
err(EXIT_FAILURE, "getcwd() failed");
}
volatile_counter = 0;
while (true) {
// Arbitrary syscall to waste system time.
if (chdir(current_dir_path) != 0) {
err(EXIT_FAILURE, "chdir() failed");
}
volatile_counter++;
if (volatile_counter == 100000) {
break;
}
}
}
static void GetResourceUsage(struct rusage *rusage) {
if (getrusage(RUSAGE_SELF, rusage) != 0) {
err(EXIT_FAILURE, "getrusage() failed");
}
}
static int GetUsedUserTimeSeconds() {
struct rusage my_rusage;
GetResourceUsage(&my_rusage);
return my_rusage.ru_utime.tv_sec;
}
static int GetUsedSystemTimeSeconds() {
struct rusage my_rusage;
GetResourceUsage(&my_rusage);
return my_rusage.ru_stime.tv_sec;
}
// This program just wastes (at least) the desired amount of CPU time, by
// checking its own resource usage (rusage) while running.
int main(int argc, char **argv) {
// Parse command-line arguments.
const char *progname = argv[0] ? argv[0] : "spend_cpu_time";
if (argc != 3) {
fprintf(stderr, "Usage: %s <user_time_seconds> <system_time_seconds>\n",
progname);
exit(EXIT_FAILURE);
}
int requested_user_time_seconds \
= atoi(argv[1]); // NOLINT(runtime/deprecated_fn)
int requested_system_time_seconds \
= atoi(argv[2]); // NOLINT(runtime/deprecated_fn)
// Waste system time first, because this also wastes some user time.
if (requested_system_time_seconds > 0) {
int spent_system_time_seconds = 0;
while (spent_system_time_seconds < requested_system_time_seconds) {
WasteSystemTime();
spent_system_time_seconds = GetUsedSystemTimeSeconds();
}
}
// Waste user time if we haven't already wasted enough.
if (requested_user_time_seconds > 0) {
int spent_user_time_seconds = 0;
while (spent_user_time_seconds < requested_user_time_seconds) {
WasteUserTime();
spent_user_time_seconds = GetUsedUserTimeSeconds();
}
}
int spent_user_time_seconds = GetUsedUserTimeSeconds();
int spent_system_time_seconds = GetUsedSystemTimeSeconds();
printf("Total user time wasted: %d seconds\n", spent_user_time_seconds);
printf("Total system time wasted: %d seconds\n", spent_system_time_seconds);
exit(EXIT_SUCCESS);
}
|
