cpufreq.chart.py: support dynamically falling back from accurate to inaccurate mode

If we switch the 'schedutil' cpufreq governor on, the 'time_in_state'
data becomes useless. And since cpufreq governors can be switched at any
time, we might as well make it possible to support transitioning between
governors without any bogus data appearing in our charts.

Before this commit, switching to 'schedutil' results in zeroed values,
and switching back to any other governor causes a huge spike datapoint
in the timeline.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

diff --git a/python.d/cpufreq.chart.py b/python.d/cpufreq.chart.py
index ef10c425143e76a42c7caccdc218e8d565e42e28..c761aae88a336cb02048725848071bbfa84c2c8b 100644 (file)
--- a/python.d/cpufreq.chart.py
+++ b/python.d/cpufreq.chart.py
@@ -4,6 +4,7 @@
 
 import glob
 import os
+import time
 from base import SimpleService
 
 # default module values (can be overridden per job in `config`)
@@ -30,20 +31,42 @@ class Service(SimpleService):
         self.definitions = CHARTS
         self._orig_name = ""
         self.assignment = {}
-        self.accurate = True
+        self.accurate_exists = True
+        self.accurate_last = {}
 
     def _get_data(self):
         data = {}
-        if self.accurate:
-            for name, path in self.assignment.items():
-                total = 0
-                for line in open(path, 'r'):
+
+        if self.accurate_exists:
+            elapsed = time.time() - self.timetable['last']
+
+            accurate_ok = True
+
+            for name, paths in self.assignment.items():
+                last = self.accurate_last[name]
+                current = 0
+                for line in open(paths['accurate'], 'r'):
                     line = list(map(int, line.split()))
-                    total += (line[0] * line[1]) / 100
-                data[name] = total
-        else:
-            for name, path in self.assignment.items():
-                data[name] = open(path, 'r').read()
+                    current += (line[0] * line[1]) / 100
+                delta = current - last
+                data[name] = delta
+                self.accurate_last[name] = current
+                if delta == 0 or abs(delta) > 1e7:
+                    # Delta is either too large or nonexistent, fall back to
+                    # less accurate reading. This can happen if we switch
+                    # to/from the 'schedutil' governor, which doesn't report
+                    # stats.
+                    accurate_ok = False
+
+            if accurate_ok:
+                return data
+            else:
+                self.alert("accurate method failed, falling back")
+
+
+        for name, paths in self.assignment.items():
+            data[name] = open(paths['inaccurate'], 'r').read()
+
         return data
 
     def check(self):
@@ -55,34 +78,29 @@ class Service(SimpleService):
         self._orig_name = self.chart_name
 
         for path in glob.glob(self.sys_dir + '/system/cpu/cpu*/cpufreq/stats/time_in_state'):
-            if len(open(path, 'rb').read().rstrip()) == 0:
-                self.alert("time_in_state is empty, broken cpufreq_stats data")
-                self.assignment = {}
-                break
             path_elem = path.split('/')
             cpu = path_elem[-4]
-            self.assignment[cpu] = path
+            if cpu not in self.assignment:
+                self.assignment[cpu] = {}
+            self.assignment[cpu]['accurate'] = path
+            self.accurate_last[cpu] = 0
 
         if len(self.assignment) == 0:
-            self.alert("trying less accurate scaling_cur_freq method")
-            self.accurate = False
+            self.accurate_exists = False
 
-            for path in glob.glob(self.sys_dir + '/system/cpu/cpu*/cpufreq/scaling_cur_freq'):
-                path_elem = path.split('/')
-                cpu = path_elem[-3]
-                self.assignment[cpu] = path
+        for path in glob.glob(self.sys_dir + '/system/cpu/cpu*/cpufreq/scaling_cur_freq'):
+            path_elem = path.split('/')
+            cpu = path_elem[-3]
+            if cpu not in self.assignment:
+                self.assignment[cpu] = {}
+            self.assignment[cpu]['inaccurate'] = path
 
         if len(self.assignment) == 0:
             self.error("couldn't find a method to read cpufreq statistics")
             return False
 
-        if self.accurate:
-            algo = 'incremental'
-        else:
-            algo = 'absolute'
-
         for name in self.assignment.keys():
-            self.definitions[ORDER[0]]['lines'].append([name, name, algo, 1, 1000])
+            self.definitions[ORDER[0]]['lines'].append([name, name, 'absolute', 1, 1000])
 
         return True