Add irqbalance plugin

The irqbalance plugin is a replacement for the bash functions
irqbalance_banned_cpus_setup and irqbalance_banned_cpus_clear. It
configures the banned CPUs in /etc/sysconfig/irqbalance. Then it
restarts irqbalance (if and only if it was previously running).

The banned CPUs can be specified as a CPU list. For example:

[irqbalance]
banned_cpus=2,4,9-13

Signed-off-by: Ondřej Lysoněk <olysonek@redhat.com>

Resolves: rhbz#1784645

tuned/consts.py

@@ -48,6 +48,9 @@ MODULES_FILE = "/etc/modprobe.d/tuned.conf"
 SYSTEMD_SYSTEM_CONF_FILE = "/etc/systemd/system.conf"
 SYSTEMD_CPUAFFINITY_VAR = "CPUAffinity"
 
+# irqbalance plugin configuration
+IRQBALANCE_SYSCONFIG_FILE = "/etc/sysconfig/irqbalance"
+
 # number of backups
 LOG_FILE_COUNT = 2
 LOG_FILE_MAXBYTES = 100*1000

tuned/plugins/plugin_irqbalance.py

@@ -0,0 +1,110 @@
+from . import base
+from .decorators import command_custom
+from tuned import consts
+import tuned.logs
+import errno
+import perf
+import re
+
+log = tuned.logs.get()
+
+class IrqbalancePlugin(base.Plugin):
+	"""
+	Plugin for irqbalance settings management.
+	"""
+
+	def __init__(self, *args, **kwargs):
+		super(IrqbalancePlugin, self).__init__(*args, **kwargs)
+		self._cpus = perf.cpu_map()
+
+	def _instance_init(self, instance):
+		instance._has_dynamic_tuning = False
+		instance._has_static_tuning = True
+
+	def _instance_cleanup(self, instance):
+		pass
+
+	@classmethod
+	def _get_config_options(cls):
+		return {
+			"banned_cpus": None,
+		}
+
+	def _read_irqbalance_sysconfig(self):
+		try:
+			with open(consts.IRQBALANCE_SYSCONFIG_FILE, "r") as f:
+				return f.read()
+		except IOError as e:
+			if e.errno == errno.ENOENT:
+				log.warn("irqbalance sysconfig file is missing. Is irqbalance installed?")
+			else:
+				log.error("Failed to read irqbalance sysconfig file: %s" % e)
+			return None
+
+	def _write_irqbalance_sysconfig(self, content):
+		try:
+			with open(consts.IRQBALANCE_SYSCONFIG_FILE, "w") as f:
+				f.write(content)
+			return True
+		except IOError as e:
+			log.error("Failed to write irqbalance sysconfig file: %s" % e)
+			return False
+
+	def _write_banned_cpus(self, sysconfig, banned_cpumask):
+		return sysconfig + "IRQBALANCE_BANNED_CPUS=%s\n" % banned_cpumask
+
+	def _clear_banned_cpus(self, sysconfig):
+		lines = []
+		for line in sysconfig.split("\n"):
+			if not re.match(r"\s*IRQBALANCE_BANNED_CPUS=", line):
+				lines.append(line)
+		return "\n".join(lines)
+
+	def _restart_irqbalance(self):
+		# Exit code 5 means unit not found (see 'EXIT_NOTINSTALLED' in
+		# systemd.exec(5))
+		retcode, out = self._cmd.execute(
+			["systemctl", "try-restart", "irqbalance"],
+			no_errors=[5])
+		if retcode != 0:
+			log.warn("Failed to restart irqbalance. Is it installed?")
+
+	def _set_banned_cpus(self, banned_cpumask):
+		content = self._read_irqbalance_sysconfig()
+		if content is None:
+			return
+		content = self._clear_banned_cpus(content)
+		content = self._write_banned_cpus(content, banned_cpumask)
+		if self._write_irqbalance_sysconfig(content):
+			self._restart_irqbalance()
+
+	def _restore_banned_cpus(self):
+		content = self._read_irqbalance_sysconfig()
+		if content is None:
+			return
+		content = self._clear_banned_cpus(content)
+		if self._write_irqbalance_sysconfig(content):
+			self._restart_irqbalance()
+
+	@command_custom("banned_cpus", per_device=False)
+	def _banned_cpus(self, enabling, value, verify, ignore_missing):
+		banned_cpumask = None
+		if value is not None:
+			banned = set(self._cmd.cpulist_unpack(value))
+			present = set(self._cpus)
+			if banned.issubset(present):
+				banned_cpumask = self._cmd.cpulist2hex(list(banned))
+			else:
+				str_cpus = ",".join([str(x) for x in self._cpus])
+				log.error("Invalid banned_cpus specified, '%s' does not match available cores '%s'"
+					  % (value, str_cpus))
+
+		if (enabling or verify) and banned_cpumask is None:
+			return None
+		if verify:
+			# Verification is currently not supported
+			return None
+		elif enabling:
+			self._set_banned_cpus(banned_cpumask)
+		else:
+			self._restore_banned_cpus()