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
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
#undef G_DISABLE_ASSERT
#undef G_LOG_DOMAIN
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/resource.h>
#include <sys/time.h>
#include <poll.h>
#define TRUE 1
#define FALSE 0
static int n_children = 3;
static int n_active_children;
static int n_iters = 10000;
static int write_fds[1024];
static struct pollfd poll_fds[1024];
void
my_pipe (int *fds)
{
if (pipe(fds) < 0)
{
int errsv = errno;
fprintf (stderr, "Cannot create pipe %s\n", strerror (errsv));
exit (1);
}
}
int
read_all (int fd, char *buf, int len)
{
size_t bytes_read = 0;
gssize count;
while (bytes_read < len)
{
count = read (fd, buf + bytes_read, len - bytes_read);
if (count < 0)
{
if (errno != EAGAIN)
return FALSE;
}
else if (count == 0)
return FALSE;
bytes_read += count;
}
return TRUE;
}
int
write_all (int fd, char *buf, int len)
{
size_t bytes_written = 0;
gssize count;
while (bytes_written < len)
{
count = write (fd, buf + bytes_written, len - bytes_written);
if (count < 0)
{
if (errno != EAGAIN)
return FALSE;
}
bytes_written += count;
}
return TRUE;
}
void
run_child (int in_fd, int out_fd)
{
int i;
int val = 1;
for (i = 0; i < n_iters; i++)
{
write_all (out_fd, (char *)&val, sizeof (val));
read_all (in_fd, (char *)&val, sizeof (val));
}
val = 0;
write_all (out_fd, (char *)&val, sizeof (val));
exit (0);
}
int
input_callback (int source, int dest)
{
int val;
if (!read_all (source, (char *)&val, sizeof(val)))
{
fprintf (stderr,"Unexpected EOF\n");
exit (1);
}
if (val)
{
write_all (dest, (char *)&val, sizeof(val));
return TRUE;
}
else
{
close (source);
close (dest);
n_active_children--;
return FALSE;
}
}
void
create_child (int pos)
{
int pid, errsv;
int in_fds[2];
int out_fds[2];
my_pipe (in_fds);
my_pipe (out_fds);
pid = fork ();
errsv = errno;
if (pid > 0) /* Parent */
{
close (in_fds[0]);
close (out_fds[1]);
write_fds[pos] = in_fds[1];
poll_fds[pos].fd = out_fds[0];
poll_fds[pos].events = POLLIN;
}
else if (pid == 0) /* Child */
{
close (in_fds[1]);
close (out_fds[0]);
setsid ();
run_child (in_fds[0], out_fds[1]);
}
else /* Error */
{
fprintf (stderr,"Cannot fork: %s\n", strerror (errsv));
exit (1);
}
}
static double
difftimeval (struct timeval *old, struct timeval *new)
{
return
(new->tv_sec - old->tv_sec) * 1000. + (new->tv_usec - old->tv_usec) / 1000;
}
int
main (int argc, char **argv)
{
int i, j;
struct rusage old_usage;
struct rusage new_usage;
if (argc > 1)
n_children = atoi(argv[1]);
if (argc > 2)
n_iters = atoi(argv[2]);
printf ("Children: %d Iters: %d\n", n_children, n_iters);
n_active_children = n_children;
for (i = 0; i < n_children; i++)
create_child (i);
getrusage (RUSAGE_SELF, &old_usage);
while (n_active_children > 0)
{
int old_n_active_children = n_active_children;
poll (poll_fds, n_active_children, -1);
for (i=0; i<n_active_children; i++)
{
if (poll_fds[i].events & (POLLIN | POLLHUP))
{
if (!input_callback (poll_fds[i].fd, write_fds[i]))
write_fds[i] = -1;
}
}
if (old_n_active_children > n_active_children)
{
j = 0;
for (i=0; i<old_n_active_children; i++)
{
if (write_fds[i] != -1)
{
if (j < i)
{
poll_fds[j] = poll_fds[i];
write_fds[j] = write_fds[i];
}
j++;
}
}
}
}
getrusage (RUSAGE_SELF, &new_usage);
printf ("Elapsed user: %g\n",
difftimeval (&old_usage.ru_utime, &new_usage.ru_utime));
printf ("Elapsed system: %g\n",
difftimeval (&old_usage.ru_stime, &new_usage.ru_stime));
printf ("Elapsed total: %g\n",
difftimeval (&old_usage.ru_utime, &new_usage.ru_utime) +
difftimeval (&old_usage.ru_stime, &new_usage.ru_stime));
printf ("total / iteration: %g\n",
(difftimeval (&old_usage.ru_utime, &new_usage.ru_utime) +
difftimeval (&old_usage.ru_stime, &new_usage.ru_stime)) /
(n_iters * n_children));
return 0;
}
|
