tools/kvm_stat: add interactive command 'r'

Provide an interactive command to reset the tracepoint statistics.
Requires some extra work for debugfs, as the counters cannot be reset.

On the up side, this offers us the opportunity to have debugfs values
reset on startup and whenever a filter is modified, becoming consistent
with the tracepoint provider. As a bonus, 'kvmstat -dt' will now provide
useful output, instead of mixing values in totally different orders of
magnitude.
Furthermore, we avoid unnecessary resets when any of the filters is
"changed" interactively to the previous value.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Acked-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

tools/kvm/kvm_stat/kvm_stat

@@ -716,15 +716,23 @@ class TracepointProvider(object):
                     ret[name] += val
         return ret
 
+    def reset(self):
+        """Reset all field counters"""
+        for group in self.group_leaders:
+            for event in group.events:
+                event.reset()
+
 
 class DebugfsProvider(object):
     """Provides data from the files that KVM creates in the kvm debugfs
     folder."""
     def __init__(self):
         self._fields = self.get_available_fields()
+        self._baseline = {}
         self._pid = 0
         self.do_read = True
         self.paths = []
+        self.reset()
 
     def get_available_fields(self):
         """"Returns a list of available fields.
@@ -741,6 +749,7 @@ class DebugfsProvider(object):
     @fields.setter
     def fields(self, fields):
         self._fields = fields
+        self.reset()
 
     @property
     def pid(self):
@@ -758,10 +767,11 @@ class DebugfsProvider(object):
             self.paths = filter(lambda x: "{}-".format(pid) in x, vms)
 
         else:
-            self.paths = ['']
+            self.paths = []
             self.do_read = True
+        self.reset()
 
-    def read(self):
+    def read(self, reset=0):
         """Returns a dict with format:'file name / field -> current value'."""
         results = {}
 
@@ -769,10 +779,22 @@ class DebugfsProvider(object):
         if not self.do_read:
             return results
 
-        for path in self.paths:
+        paths = self.paths
+        if self._pid == 0:
+            paths = []
+            for entry in os.walk(PATH_DEBUGFS_KVM):
+                for dir in entry[1]:
+                    paths.append(dir)
+        for path in paths:
             for field in self._fields:
-                results[field] = results.get(field, 0) \
-                                 + self.read_field(field, path)
+                value = self.read_field(field, path)
+                key = path + field
+                if reset:
+                    self._baseline[key] = value
+                if self._baseline.get(key, -1) == -1:
+                    self._baseline[key] = value
+                results[field] = (results.get(field, 0) + value -
+                                  self._baseline.get(key, 0))
 
         return results
 
@@ -786,6 +808,11 @@ class DebugfsProvider(object):
         except IOError:
             return 0
 
+    def reset(self):
+        """Reset field counters"""
+        self._baseline = {}
+        self.read(1)
+
 
 class Stats(object):
     """Manages the data providers and the data they provide.
@@ -822,12 +849,18 @@ class Stats(object):
         for provider in self.providers:
             provider.pid = self._pid_filter
 
+    def reset(self):
+        self.values = {}
+        for provider in self.providers:
+            provider.reset()
+
     @property
     def fields_filter(self):
         return self._fields_filter
 
     @fields_filter.setter
     def fields_filter(self, fields_filter):
+        if fields_filter != self._fields_filter:
             self._fields_filter = fields_filter
             self.update_provider_filters()
 
@@ -837,6 +870,7 @@ class Stats(object):
 
     @pid_filter.setter
     def pid_filter(self, pid):
+        if pid != self._pid_filter:
             self._pid_filter = pid
             self.values = {}
             self.update_provider_pid()
@@ -847,11 +881,9 @@ class Stats(object):
         for provider in self.providers:
             new = provider.read()
             for key in provider.fields:
-                oldval = self.values.get(key, (0, 0))
+                oldval = self.values.get(key, (0, 0))[0]
                 newval = new.get(key, 0)
-                newdelta = None
-                if oldval is not None:
-                    newdelta = newval - oldval[0]
+                newdelta = newval - oldval
                 self.values[key] = (newval, newdelta)
         return self.values
 
@@ -1117,6 +1149,10 @@ class Tui(object):
                 if char == 'p':
                     self.show_vm_selection_by_pid()
                     sleeptime = DELAY_INITIAL
+                if char == 'r':
+                    self.refresh_header()
+                    self.stats.reset()
+                    sleeptime = DELAY_INITIAL
             except KeyboardInterrupt:
                 break
             except curses.error:
@@ -1190,6 +1226,7 @@ Interactive Commands:
    p     filter by PID
    q     quit
    x     toggle reporting of stats for individual child trace events
+   r     reset stats
 Press any other key to refresh statistics immediately.
 """
 

tools/kvm/kvm_stat/kvm_stat.txt

@@ -39,6 +39,8 @@ INTERACTIVE COMMANDS
 
 *q*::	quit
 
+*r*::	reset stats
+
 *x*::	toggle reporting of stats for child trace events
 
 Press any other key to refresh statistics immediately.