scripts/kvm/kvm_stat: Introduce main function

The main function should be the main location for initialization and
helps encapsulating variables into a scope. This way they don't have
to be global and might be mistaken for local ones.

As the providers variable is scoped now it can't be accessed from
within the Stats class. Hence, the global access to the variable was
changed to a local one.

Reviewed-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Message-Id: <1452525484-32309-10-git-send-email-frankja@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 82 insertions, 71 deletions

diff --git a/scripts/kvm/kvm_stat b/scripts/kvm/kvm_stat
index 6f0692d..9f943ef 100755
--- a/scripts/kvm/kvm_stat
+++ b/scripts/kvm/kvm_stat
@@ -285,8 +285,6 @@ def detect_platform():
                     s390_init()
                     return
 
-detect_platform()
-
 
 def walkdir(path):
     """Returns os.walk() data for specified directory.
@@ -453,7 +451,7 @@ class Stats:
                 return True
             return re.match(self.fields_filter, key) is not None
         self.values = dict()
-        for d in providers:
+        for d in self.providers:
             provider_fields = [key for key in d.fields() if wanted(key)]
             for key in provider_fields:
                 self.values[key] = None
@@ -462,7 +460,7 @@ class Stats:
         self.fields_filter = fields_filter
         self._update()
     def get(self):
-        for d in providers:
+        for d in self.providers:
             new = d.read()
             for key in d.fields():
                 oldval = self.values.get(key, (0, 0))
@@ -473,20 +471,6 @@ class Stats:
                 self.values[key] = (newval, newdelta)
         return self.values
 
-if not os.path.exists('/sys/kernel/debug'):
-    sys.stderr.write('Please enable CONFIG_DEBUG_FS in your kernel.')
-    sys.exit(1)
-if not os.path.exists(PATH_DEBUGFS_KVM):
-    sys.stderr.write("Please make sure, that debugfs is mounted and "
-                     "readable by the current user:\n"
-                     "('mount -t debugfs debugfs /sys/kernel/debug')\n"
-                     "Also ensure, that the kvm modules are loaded.\n")
-    sys.exit(1)
-if not os.path.exists(PATH_DEBUGFS_TRACING):
-    sys.stderr.write("Please make {0} readable by the current user.\n"
-                     .format(PATH_DEBUGFS_TRACING))
-    sys.exit(1)
-
 LABEL_WIDTH = 40
 NUMBER_WIDTH = 10
 
@@ -576,56 +560,83 @@ def log(stats):
         statline()
         line += 1
 
-options = optparse.OptionParser()
-options.add_option('-1', '--once', '--batch',
-                   action = 'store_true',
-                   default = False,
-                   dest = 'once',
-                   help = 'run in batch mode for one second',
-                   )
-options.add_option('-l', '--log',
-                   action = 'store_true',
-                   default = False,
-                   dest = 'log',
-                   help = 'run in logging mode (like vmstat)',
-                   )
-options.add_option('-t', '--tracepoints',
-                   action = 'store_true',
-                   default = False,
-                   dest = 'tracepoints',
-                   help = 'retrieve statistics from tracepoints',
-                   )
-options.add_option('-d', '--debugfs',
-                   action = 'store_true',
-                   default = False,
-                   dest = 'debugfs',
-                   help = 'retrieve statistics from debugfs',
-                   )
-options.add_option('-f', '--fields',
-                   action = 'store',
-                   default = None,
-                   dest = 'fields',
-                   help = 'fields to display (regex)',
-                   )
-(options, args) = options.parse_args(sys.argv)
-
-providers = []
-if options.tracepoints:
-    providers.append(TracepointProvider())
-if options.debugfs:
-    providers.append(DebugfsProvider())
-
-if len(providers) == 0:
-    try:
-        providers = [TracepointProvider()]
-    except:
-        providers = [DebugfsProvider()]
-
-stats = Stats(providers, fields = options.fields)
-
-if options.log:
-    log(stats)
-elif not options.once:
-    curses.wrapper(tui, stats)
-else:
-    batch(stats)
+def get_options():
+    optparser = optparse.OptionParser()
+    optparser.add_option('-1', '--once', '--batch',
+                         action = 'store_true',
+                         default = False,
+                         dest = 'once',
+                         help = 'run in batch mode for one second',
+                         )
+    optparser.add_option('-l', '--log',
+                         action = 'store_true',
+                         default = False,
+                         dest = 'log',
+                         help = 'run in logging mode (like vmstat)',
+                         )
+    optparser.add_option('-t', '--tracepoints',
+                         action = 'store_true',
+                         default = False,
+                         dest = 'tracepoints',
+                         help = 'retrieve statistics from tracepoints',
+                         )
+    optparser.add_option('-d', '--debugfs',
+                         action = 'store_true',
+                         default = False,
+                         dest = 'debugfs',
+                         help = 'retrieve statistics from debugfs',
+                         )
+    optparser.add_option('-f', '--fields',
+                         action = 'store',
+                         default = None,
+                         dest = 'fields',
+                         help = 'fields to display (regex)',
+                         )
+    (options, _) = optparser.parse_args(sys.argv)
+    return options
+
+def get_providers(options):
+    providers = []
+
+    if options.tracepoints:
+        providers.append(TracepointProvider())
+    if options.debugfs:
+        providers.append(DebugfsProvider())
+    if len(providers) == 0:
+        providers.append(TracepointProvider())
+
+    return providers
+
+def check_access():
+    if not os.path.exists('/sys/kernel/debug'):
+        sys.stderr.write('Please enable CONFIG_DEBUG_FS in your kernel.')
+        sys.exit(1)
+
+    if not os.path.exists(PATH_DEBUGFS_KVM):
+        sys.stderr.write("Please make sure, that debugfs is mounted and "
+                         "readable by the current user:\n"
+                         "('mount -t debugfs debugfs /sys/kernel/debug')\n"
+                         "Also ensure, that the kvm modules are loaded.\n")
+        sys.exit(1)
+
+    if not os.path.exists(PATH_DEBUGFS_TRACING):
+        sys.stderr.write("Please make {0} readable by the current user.\n"
+                         .format(PATH_DEBUGFS_TRACING))
+        sys.exit(1)
+
+def main():
+    check_access()
+    detect_platform()
+    options = get_options()
+    providers = get_providers(options)
+    stats = Stats(providers, fields = options.fields)
+
+    if options.log:
+        log(stats)
+    elif not options.once:
+        curses.wrapper(tui, stats)
+    else:
+        batch(stats)
+
+if __name__ == "__main__":
+    main()