strange performance numbers

[Tim Flechtner <timf trdlnk com>]

we have been seeing some very odd differences in cpu utilization for a
simple test application (code attached) on different solaris 8 x86 hosts.

we have two boxes with identical modeled graphics cards:
red -
  a 2.53 Ghz P4, 533 Mhz front side bus with 512 MB DDR RAM running 
solaris 8 (x86)
protea -
  a 2.0 Ghz P4, 400 Mhz front side bus with 512 MB SDRAM running 
solaris 8 (x86)



the test application performs screen updates every time a timeout signal
of the specified interval fires.
a screen update consists of updating four text cells of a tree view.
interval is the time in miliseconds between screen updates.

interval   red   protea
1000       0.02  0.02
100        0.05  0.05
10         0.07  1.50

can anyone suggest why protea's (admittedly a lower power machine) cpu 
usage would shoot up so dramatically under the heavier load?

thanks!
-tim

#include <gtk/gtk.h>

enum {
  FIRST_COLUMN,
  SECOND_COLUMN,
  NUM_COLUMNS
};

GtkTreeIter row1, row2;
GValue v11, v12, v21, v22;
GtkTreeStore* model;
int sleepytime;

int on_timeout(gpointer data)
{
  static int i = 0;

  /* need to schedule another callback and return */
  g_value_set_int(&v11, i++);
  gtk_tree_store_set_value(model, &row1, 0, &v11);
  g_value_set_int(&v12, i++);
  gtk_tree_store_set_value(model, &row1, 1, &v12);
  g_value_set_int(&v21, i++);
  gtk_tree_store_set_value(model, &row2, 0, &v21);
  g_value_set_int(&v22, i++);
  gtk_tree_store_set_value(model, &row2, 1, &v22);
  
  return TRUE;
}

void callback(GtkWidget* widget, gpointer data)
{
  gtk_timeout_add(sleepytime, on_timeout, NULL);
  return;
}

main(int argc, char** argv)
{
  GtkWidget* view;
  GtkTreeViewColumn* column;
  GtkCellRenderer* cell_renderer;
  GtkWidget* window;
  GtkWidget* vbox;
  GtkWidget* button;
  int i, j;

  if(argc < 2) {
    sleepytime = 1000;
  } else {
    sleepytime = atoi(argv[1]);
  }
  
  gtk_init(&argc, &argv);
  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  vbox = gtk_vbox_new(FALSE, 0);

  g_signal_connect(G_OBJECT(window), "destroy",
            G_CALLBACK(gtk_main_quit),
			NULL);

  model = gtk_tree_store_new(NUM_COLUMNS, G_TYPE_INT, G_TYPE_INT);
  // custom_populate_model_function(model);
  view = gtk_tree_view_new_with_model(GTK_TREE_MODEL(model));
  cell_renderer = gtk_cell_renderer_text_new();
  g_object_set(G_OBJECT (cell_renderer),
               "foreground", "dodger blue",
			   NULL);
  column = gtk_tree_view_column_new_with_attributes(
      "Column 1", cell_renderer, "text", FIRST_COLUMN, NULL);
  gtk_tree_view_append_column(GTK_TREE_VIEW(view), column);
  cell_renderer = gtk_cell_renderer_text_new();
  g_object_set(G_OBJECT (cell_renderer),
               "weight", "bold",
			   NULL);
  column = gtk_tree_view_column_new_with_attributes(
      "Column 2", cell_renderer, "text", SECOND_COLUMN, NULL);
  gtk_tree_view_append_column(GTK_TREE_VIEW(view), column);
  g_object_unref(G_OBJECT(model));

  // Build the button
  // ----------------
  button = gtk_button_new_with_label("Thump CPU");
  g_signal_connect(G_OBJECT(button), "clicked",
            G_CALLBACK(callback), (gpointer) "Thump CPU");

  gtk_box_pack_start(GTK_BOX(vbox), view, TRUE, TRUE, 0);
  gtk_box_pack_start(GTK_BOX(vbox), button, TRUE, TRUE, 0);
  gtk_container_add(GTK_CONTAINER(window), vbox);

  // Add some rows
  // -------------
  gtk_tree_store_append(model, &row1, NULL);
  gtk_tree_store_append(model, &row2, NULL);

  memset(&v11, 0, sizeof(GValue));
  g_value_init(&v11, G_TYPE_INT);
  memset(&v12, 0, sizeof(GValue));
  g_value_init(&v12, G_TYPE_INT);
  memset(&v21, 0, sizeof(GValue));
  g_value_init(&v21, G_TYPE_INT);
  memset(&v22, 0, sizeof(GValue));
  g_value_init(&v22, G_TYPE_INT);

  gtk_widget_show_all(window);
  gtk_main();

  return 0;
}

CC = gcc

#CFLAGS = -Wall			 	\
#	-DG_DISABLE_DEPRECATED 	 	\
#	-DGDK_DISABLE_DEPRECATED 	\
#	-DGDK_PIXBUF_DISABLE_DEPRECATED \
#	-DGTK_DISABLE_DEPRECATED

CFLAGS = 

tree: tree.c 
	$(CC) tree.c -o tree $(CFLAGS) `pkg-config gtk+-2.0 --cflags --libs`

clean: 
	rm -f *.o tree