tools/kvm_stat: add new command line switch '-i'

It might be handy to display the full history of event stats to compare
the current event distribution against any available historic data.
Since we have that available for debugfs, we offer a respective command
line option to display what's available.
Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/kvm/kvm_stat/kvm_stat

@@ -681,12 +681,14 @@ class TracepointProvider(Provider):
 class DebugfsProvider(Provider):
     """Provides data from the files that KVM creates in the kvm debugfs
     folder."""
-    def __init__(self, pid, fields_filter):
+    def __init__(self, pid, fields_filter, include_past):
         self.update_fields(fields_filter)
         self._baseline = {}
         self.do_read = True
         self.paths = []
         self.pid = pid
+        if include_past:
+            self.restore()
 
     def get_available_fields(self):
         """"Returns a list of available fields.
@@ -730,7 +732,14 @@ class DebugfsProvider(Provider):
         self.reset()
 
     def read(self, reset=0):
-        """Returns a dict with format:'file name / field -> current value'."""
+        """Returns a dict with format:'file name / field -> current value'.
+
+        Parameter 'reset':
+          0   plain read
+          1   reset field counts to 0
+          2   restore the original field counts
+
+        """
         results = {}
 
         # If no debugfs filtering support is available, then don't read.
@@ -747,8 +756,10 @@ class DebugfsProvider(Provider):
             for field in self._fields:
                 value = self.read_field(field, path)
                 key = path + field
-                if reset:
+                if reset == 1:
                     self._baseline[key] = value
+                if reset == 2:
+                    self._baseline[key] = 0
                 if self._baseline.get(key, -1) == -1:
                     self._baseline[key] = value
                 results[field] = (results.get(field, 0) + value -
@@ -771,6 +782,11 @@ class DebugfsProvider(Provider):
         self._baseline = {}
         self.read(1)
 
+    def restore(self):
+        """Reset field counters"""
+        self._baseline = {}
+        self.read(2)
+
 
 class Stats(object):
     """Manages the data providers and the data they provide.
@@ -791,7 +807,8 @@ class Stats(object):
         providers = []
 
         if options.debugfs:
-            providers.append(DebugfsProvider(options.pid, options.fields))
+            providers.append(DebugfsProvider(options.pid, options.fields,
+                                             options.dbgfs_include_past))
         if options.tracepoints or not providers:
             providers.append(TracepointProvider(options.pid, options.fields))
 
@@ -1270,6 +1287,8 @@ class Tui(object):
                     sleeptime = self._delay_initial
                 if char == 'x':
                     self.update_drilldown()
+                    # prevents display of current values on next refresh
+                    self.stats.get()
             except KeyboardInterrupt:
                 break
             except curses.error:
@@ -1381,6 +1400,13 @@ Press any other key to refresh statistics immediately.
                          dest='once',
                          help='run in batch mode for one second',
                          )
+    optparser.add_option('-i', '--debugfs-include-past',
+                         action='store_true',
+                         default=False,
+                         dest='dbgfs_include_past',
+                         help='include all available data on past events for '
+                              'debugfs',
+                         )
     optparser.add_option('-l', '--log',
                          action='store_true',
                          default=False,

tools/kvm/kvm_stat/kvm_stat.txt

@@ -70,6 +70,10 @@ OPTIONS
 --debugfs::
 	retrieve statistics from debugfs
 
+-i::
+--debugfs-include-past::
+	include all available data on past events for debugfs
+
 -p<pid>::
 --pid=<pid>::
 	limit statistics to one virtual machine (pid)