> Going back to your original point, it is definitely not a
> "busy wait".
I just rolled together a quick test... A GTK main loop running two "sources".
First an "event source" created using g_timeout_add() that prints the current
count each second, and halting the program (via gtk_main_quit() ) after the
10th count.
Second, an idle event crated though g_idle_add() that simply increments said
counter and returns true to repeat (similar to what you'd have watching for a
flag indicating a Unix signal had occured).
The program ran for 10 seconds, giving counts of:
** Message: Ticker Tocker... 9 -> 160565
** Message: Ticker Tocker... 8 -> 343367
** Message: Ticker Tocker... 7 -> 545729
** Message: Ticker Tocker... 6 -> 703564
** Message: Ticker Tocker... 5 -> 856554
** Message: Ticker Tocker... 4 -> 1018223
** Message: Ticker Tocker... 3 -> 1219280
** Message: Ticker Tocker... 2 -> 1390704
** Message: Ticker Tocker... 1 -> 1548533
My CPU usage graph applet showed a 100% CPU burn during that time, however
oddly the output of the system "time" command showed:
real:10.587s user:2.172s sys:7.224s
If that means anything useful. I'm guessing from that that the program is
spending a good deal of its time in select(), with a zero timeout (causing it
to return immediately each time).
That's well over 1548533 executions (I forgot to print the counter after the
10th second) of the idle callback, or 172059 calls to the idler function per
second.
Personally, I'd call that a busy wait.
The source code to my little test program (incase I did something very very
wrong), goes something like this:
#include <gtk/gtk.h>
gint count_down = 10, iterations = 0;
gboolean tickertocker() {
if ( --count_down <= 0 ) {
g_message("Countdown go kabloowie!");
gtk_main_quit();
return;
}
g_message("Ticker Tocker... %i -> %i", count_down, iterations);
return TRUE;
}
gboolean idle_function() {
++iterations;
return TRUE;
}
int main(int argc, char* argv[]) {
// Initialize the widget set
gtk_set_locale();
gtk_init(&argc, &argv);
// Initialize application components
g_timeout_add(1000, (GSourceFunc) tickertocker, NULL);
g_idle_add( (GSourceFunc) idle_function, NULL);
// Enter the main event loop
gtk_main();
// Shutdown application components
return 0;
}
Fredderic
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