instrument/schedstats: Add initial instrument for schedstats

Author: Brendan Jackman

devlib/__init__.py

@@ -16,6 +16,7 @@
 from devlib.instrument.hwmon import HwmonInstrument
 from devlib.instrument.monsoon import MonsoonInstrument
 from devlib.instrument.netstats import NetstatsInstrument
+from devlib.instrument.schedstats import SchedstatsInstrument
 
 from devlib.trace.ftrace import FtraceCollector
 

devlib/instrument/schedstats.py

@@ -0,0 +1,204 @@
+#    Copyright 2017 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from collections import OrderedDict
+import logging
+import re
+
+from devlib.instrument import (Instrument, INSTANTANEOUS,
+                               Measurement, MeasurementType)
+from devlib.exception import TargetError
+
+# Each entry in schedstats has a space-separated list of fields. DOMAIN_MEASURES
+# and CPU_MEASURES are the fields for domain entries and CPU entries
+# resepectively.
+#
+# See kernel/sched/stat.c and Documentation/scheduler/sched-stats.txt
+#
+# The names used here are based on the identifiers in the scheduler code.
+
+# Some domain fields are repeated for each idle type
+DOMAIN_MEASURES = []
+for idle_type in ['CPU_IDLE', 'CPU_NOT_IDLE', 'CPU_NEWLY_IDLE']:
+    for lb_measure in [
+            'lb_count',
+            'lb_balanced',
+            'lb_failed',
+            'lb_imbalance',
+            'lb_gained',
+            'lb_hot_gained',
+            'lb_nobusyq',
+            'lb_nobusyg']:
+        DOMAIN_MEASURES.append('{}:{}'.format(lb_measure, idle_type))
+
+DOMAIN_MEASURES += [
+    'alb_count',
+    'alb_failed',
+    'alb_pushed',
+    'sbe_count',
+    'sbe_balanced',
+    'sbe_pushed',
+    'sbf_count',
+    'sbf_balanced',
+    'sbf_pushed',
+    'ttwu_wake_remote',
+    'ttwu_move_affine',
+    'ttwu_move_balance'
+]
+
+CPU_MEASURES = [
+    'yld_count',
+    'legacy_always_zero',
+    'schedule_count',
+    'sched_goidle',
+    'ttwu_count',
+    'ttwu_local',
+    'rq_cpu_time',
+    'run_delay',
+    'pcount'
+]
+
+class SchedstatsInstrument(Instrument):
+    """
+    An instrument for parsing Linux's schedstats
+
+    Creates a *site* for each CPU and each sched_domain (i.e. for each line of
+    /proc/schedstat), and a *channel* for each item in the schedstats file. For
+    example a *site* named "cpu0" will be created for the scheduler stats on
+    CPU0 and a *site* named "cpu0domain0" will be created for the scheduler
+    stats on CPU0's first-level scheduling domain.
+
+    For example:
+
+     - If :method:`reset` is called with ``sites=['cpu0']`` then all
+       stats will be collected for CPU0's runqueue, with a channel for each
+       statistic.
+
+     - If :method:`reset` is called with ``kinds=['alb_pushed']`` then the count
+       of migrations successfully triggered by active_load_balance will be
+       colelcted for each sched domain, with a channel for each domain.
+
+    The measurements are named according to corresponding identifiers in the
+    kernel scheduler code. The names for ``sched_domain.lb_*`` stats, which are
+    recorded per ``cpu_idle_type`` are suffixed with a ':' followed by the idle
+    type, for example ``'lb_balanced:CPU_NEWLY_IDLE'``.
+
+    Only supports schedstats version 15.
+
+    Only supports the CPU and domain data in /proc/schedstat, not the per-task
+    data under /proc/<pid>/schedstat.
+    """
+
+    mode = INSTANTANEOUS
+
+    sysctl_path = '/proc/sys/kernel/sched_schedstats'
+    schedstat_path = '/proc/schedstat'
+
+    def __init__(self, *args, **kwargs):
+        super(SchedstatsInstrument, self).__init__(*args, **kwargs)
+        self.logger = logging.getLogger(self.__class__.__name__)
+
+        try:
+            self.old_sysctl_value = self.target.read_int(self.sysctl_path)
+        except TargetError:
+            if not self.target.file_exists(self.sysctl_path):
+                raise TargetError('schedstats not supported by target. '
+                                  'Ensure CONFIG_SCHEDSTATS is enabled.')
+
+        self.target.write_value(self.sysctl_path, 1)
+
+        # Check version matches
+        lines = self.target.read_value(self.schedstat_path).splitlines()
+        match = re.search(r'version ([0-9]+)', lines[0])
+        if not match or match.group(1) != '15':
+            raise TargetError(
+                'Unsupported schedstat version string: "{}"'.format(lines[0]))
+
+        # Take a sample of the schedstat file to figure out which channels to
+        # create.
+        # We'll create a site for each CPU and a site for each sched_domain.
+        for site, measures in self._get_sample().iteritems():
+            if site.startswith('cpu'):
+                measurement_category = 'schedstat_cpu'
+            else:
+                measurement_category = 'schedstat_domain'
+
+            for measurement_name in measures.keys():
+                # TODO: constructing multiple MeasurementTypes with same
+                # params. Does it matter?
+                measurement_type = MeasurementType(
+                    measurement_name, '', measurement_category)
+                self.add_channel(site=site,
+                                 name='{}_{}'.format(site, measurement_name),
+                                 measure=measurement_type)
+
+    def teardown(self):
+        self.target.write_value(self.sysctl_path, self.old_sysctl_value)
+
+    def _get_sample(self):
+        lines = self.target.read_value(self.schedstat_path).splitlines()
+        ret = OrderedDict()
+
+        # Example /proc/schedstat contents:
+        #
+        # version 15
+        # timestamp <timestamp>
+        # cpu0 <cpu fields>
+        # domain0 <domain fields>
+        # domain1 <domain fields>
+        # cpu1 <cpu_fields>
+        # domain0 <domain fields>
+        # domain1 <domain fields>
+
+        curr_cpu = None
+        for line in lines[2:]:
+            tokens = line.split()
+            if tokens[0].startswith('cpu'):
+                curr_cpu = tokens[0]
+                site = curr_cpu
+                measures = CPU_MEASURES
+                tokens = tokens[1:]
+            elif tokens[0].startswith('domain'):
+                if not curr_cpu:
+                    raise TargetError(
+                        'Failed to parse schedstats, found domain before CPU')
+                # We'll name the site for the domain like "cpu0domain0"
+                site = curr_cpu + tokens[0]
+                measures = DOMAIN_MEASURES
+                tokens = tokens[2:]
+            else:
+                self.logger.warning(
+                    'Unrecognised schedstats line: "{}"'.format(line))
+                continue
+
+            values = [int(t) for t in tokens]
+            if len(values) != len(measures):
+                raise TargetError(
+                    'Unexpected length for schedstat line "{}"'.format(line))
+            ret[site] = OrderedDict(zip(measures, values))
+
+        return ret
+
+    def take_measurement(self):
+        ret = []
+        sample = self._get_sample()
+
+        for channel in self.active_channels:
+            value = sample[channel.site][channel.kind]
+            ret.append(Measurement(value, channel))
+
+        return ret
+
+