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#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <glib.h>
static int n_children = 3;
static int n_active_children;
static int n_iters = 10000;
static GMainLoop *loop;
void
io_pipe (GIOChannel **channels)
{
int fds[2];
if (pipe(fds) < 0)
{
fprintf (stderr, "Cannot create pipe %s\n", g_strerror (errno));
exit (1);
}
channels[0] = g_io_channel_unix_new (fds[0]);
channels[1] = g_io_channel_unix_new (fds[1]);
}
gboolean
read_all (GIOChannel *channel, char *buf, int len)
{
int bytes_read = 0;
int count;
GIOError err;
while (bytes_read < len)
{
err = g_io_channel_read (channel, buf + bytes_read, len - bytes_read, &count);
if (err)
{
if (err != G_IO_ERROR_AGAIN)
return FALSE;
}
else if (count == 0)
return FALSE;
bytes_read += count;
}
return TRUE;
}
gboolean
write_all (GIOChannel *channel, char *buf, int len)
{
int bytes_written = 0;
int count;
GIOError err;
while (bytes_written < len)
{
err = g_io_channel_write (channel, buf + bytes_written, len - bytes_written, &count);
if (err && err != G_IO_ERROR_AGAIN)
return FALSE;
bytes_written += count;
}
return TRUE;
}
void
run_child (GIOChannel *in_channel, GIOChannel *out_channel)
{
int i;
int val = 1;
GTimer *timer = g_timer_new();
for (i = 0; i < n_iters; i++)
{
write_all (out_channel, (char *)&val, sizeof (val));
read_all (in_channel, (char *)&val, sizeof (val));
}
val = 0;
write_all (out_channel, (char *)&val, sizeof (val));
val = g_timer_elapsed (timer, NULL) * 1000;
write_all (out_channel, (char *)&val, sizeof (val));
g_timer_destroy (timer);
exit (0);
}
gboolean
input_callback (GIOChannel *source,
GIOCondition condition,
gpointer data)
{
int val;
GIOChannel *dest = (GIOChannel *)data;
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
{
g_io_channel_close (source);
g_io_channel_close (dest);
g_io_channel_unref (source);
g_io_channel_unref (dest);
n_active_children--;
if (n_active_children == 0)
g_main_loop_quit (loop);
return FALSE;
}
}
void
create_child ()
{
int pid;
GIOChannel *in_channels[2];
GIOChannel *out_channels[2];
io_pipe (in_channels);
io_pipe (out_channels);
pid = fork ();
if (pid > 0) /* Parent */
{
g_io_channel_close (in_channels[0]);
g_io_channel_close (out_channels[1]);
g_io_add_watch (out_channels[0], G_IO_IN | G_IO_HUP,
input_callback, in_channels[1]);
}
else if (pid == 0) /* Child */
{
g_io_channel_close (in_channels[1]);
g_io_channel_close (out_channels[0]);
setsid ();
run_child (in_channels[0], out_channels[1]);
}
else /* Error */
{
fprintf (stderr, "Cannot fork: %s\n", g_strerror (errno));
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;
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 ();
getrusage (RUSAGE_SELF, &old_usage);
loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (loop);
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;
}
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