plugin_scheduler: make perf support optional

Requested in: https://src.fedoraproject.org/rpms/tuned/pull-request/8

Signed-off-by: Jaroslav Škarvada <jskarvad@redhat.com>

tuned.spec

@@ -83,7 +83,7 @@ BuildRequires: %{_py}-mock
 %endif
 BuildRequires: %{_py}-pyudev
 Requires: %{_py}-pyudev
-Requires: %{_py}-linux-procfs, %{_py}-perf
+Requires: %{_py}-linux-procfs
 Requires: %{_py}-inotify
 %if %{without python3}
 Requires: %{_py}-schedutils
@@ -93,9 +93,6 @@ Requires: %{_py}-schedutils
 # BuildRequires for 'make test'
 BuildRequires: python3-dbus, python3-gobject-base
 Requires: python3-dbus, python3-gobject-base
-%if 0%{?fedora} > 22 || 0%{?rhel} > 7
-Recommends: dmidecode
-%endif
 %else
 # BuildRequires for 'make test'
 BuildRequires: dbus-python, pygobject3-base
@@ -105,11 +102,15 @@ Requires: virt-what, ethtool, gawk
 Requires: util-linux, dbus, polkit
 %if 0%{?fedora} > 22 || 0%{?rhel} > 7
 Recommends: dmidecode
+# https://src.fedoraproject.org/rpms/tuned/pull-request/8
+Recommends: %{_py}-perf
 # i686 excluded
 Recommends: kernel-tools
 Requires: hdparm
 Requires: kmod
 Requires: iproute
+%else
+Requires: %{_py}-perf
 %endif
 # syspurpose
 %if 0%{?rhel} > 8

tuned/consts.py

@@ -77,6 +77,9 @@ ACPI_DIR = "/sys/firmware/acpi"
 # built-in functions configuration
 SYSFS_CPUS_PATH = "/sys/devices/system/cpu"
 
+# present CPUs
+SYSFS_CPUS_PRESENT_PATH = "%s/present" % SYSFS_CPUS_PATH
+
 # number of backups
 LOG_FILE_COUNT = 2
 LOG_FILE_MAXBYTES = 100*1000

tuned/plugins/plugin_scheduler.py

@@ -8,7 +8,12 @@ import tuned.logs
 import re
 from subprocess import *
 import threading
-import perf
+# perf is optional
+try:
+	import perf
+except ModuleNotFoundError:
+# if perf is unavailable, it will be disabled later
+	pass
 import select
 import tuned.consts as consts
 import procfs
@@ -449,7 +454,15 @@ class SchedulerPlugin(base.Plugin):
 		self._ps_whitelist = ".*"
 		self._ps_blacklist = ""
 		self._cgroup_ps_blacklist_re = ""
-		self._cpus = perf.cpu_map()
+		# perf is optional, if unavailable, it will be disabled later
+		try:
+			self._cpus = perf.cpu_map()
+		except (NameError, AttributeError):
+			cpus = self._cmd.read_file(consts.SYSFS_CPUS_PRESENT_PATH)
+			# it's different type than perf.cpu_map(), but without perf we use it as iterable
+			# which should be compatible, fallback to single core CPU if sysfs is unavailable
+			self._cpus = self._cmd.cpulist_unpack(cpus) if cpus else [ 0 ]
+
 		self._scheduler_storage_key = self._storage_key(
 				command_name = "scheduler")
 		self._irq_process = True
@@ -534,6 +547,8 @@ class SchedulerPlugin(base.Plugin):
 					instance._evlist.mmap(pages = perf_mmap_pages)
 			# no perf
 			except:
+				log.warning("python-perf unavailable, disabling perf support and " \
+					"runtime tuning, you can try to (re)install python(3)-perf package")
 				instance._runtime_tuning = False
 
 	def _instance_cleanup(self, instance):