--- /usr/bin/emerge	2008-05-03 21:49:13.000000000 +0200
+++ /usr/bin/emerge	2008-05-03 21:48:03.000000000 +0200
@@ -6617,6 +6617,34 @@ 
 		settings["NOCOLOR"] = "true"
 		settings.backup_changes("NOCOLOR")
 
+def ionice(io_class, io_prio, pid = -1):
+	"""Execute the program ionice to adapt io performance"""
+
+	# Only the root user can use ionice
+	if os.getuid() != 0:
+		return False   # Failed not root
+
+	# Determine the process id to change
+	if pid == -1:
+		npid = os.getpid()
+	else:
+		npid = pid
+
+	# Search ionice executable in PATH
+	ionice_bin = None
+	for path in os.environ["PATH"].split(":"):
+		file = os.path.join(path, "ionice")
+		if os.path.exists(file):
+			ionice_bin = file
+			break
+	if ionice_bin is None:
+		return False   # Failed binary not installed
+
+	# Execute the ionice program
+	rv = os.system("%s -c%d -n%d -p%d >/dev/null 2>&1" % \
+		(ionice_bin, io_class, io_prio, npid))
+	return rv == 0
+
 def emerge_main():
 	# Disable color until we're sure that it should be enabled (after
 	# EMERGE_DEFAULT_OPTS has been parsed).
@@ -6636,6 +6664,23 @@ 
 	settings, trees, mtimedb = load_emerge_config()
 	portdb = trees[settings["ROOT"]]["porttree"].dbapi
 
+	# Use ionice to amend the performance or responsivness of the system
+	io_class_dict = {"realtime":1, "besteffort":2, "idle":3, "1":1, "2":2, "3":3, "none":-1}
+	try:
+		io_class = io_class_dict[settings.get("PORTAGE_IONICE_CLASS", "none")]
+		io_prio = int(settings.get("PORTAGE_IONICE_PRIO", "4"))
+		if io_prio < 0: raise ValueError
+		if io_prio > 7: raise ValueError
+	except (KeyError, ValueError), e:
+		portage.writemsg("!!! Invalid value in PORTAGE_IONICE_CLASS or PORTAGE_IONICE_PRIO\n")
+		portage.writemsg("!!! PORTAGE_IONICE_CLASS=<realtime|besteffort|idle>\n")
+		portage.writemsg("!!! PORTAGE_IONICE_PRIO=<0..7>\n")
+		io_class = -1
+		io_prio = -1
+		del e
+	if io_class != -1 and io_prio != -1:
+		ionice(io_class, io_prio)
+
 	try:
 		os.nice(int(settings.get("PORTAGE_NICENESS", "0")))
 	except (OSError, ValueError), e: