tuna_gui: add command line option to explicitly disable perf usage

Add command line option (-d, --disable_perf) to explicitly disable
usage of perf facility for procview. Previously if the perf attach
succeeds, it will always be used. Now if -d is passed it will be not
tried.

Default behaviour is kept as before.

Rationale for adding this option:
-) On very loaded systems (mostly with processes / threads varing very
often) perf may end up being triggered all the time, causing a
continuous widget refresh which will cause 100% CPU usage of tuna
and therefore a very sluggish and hardly usable GUI. This can be in
case partially alleviated by reducing the refresh time via the
recently added refresh time option.
-) As it is now (maybe we could change?) perf doesn't deliver the
same data as polling /proc does, for example perf will not update
context switch data. So having the possibility for the user to go
anyway for acquiring data from /proc (as ugly as polling is) to have
also that data displayed, if needed, sounds like a reasonable
approach.

Signed-off-by: Federico Pellegrin <fede@evolware.org>
Signed-off-by: John Kacur <jkacur@redhat.com>

4 files changed, 20 insertions, 10 deletions

diff --git a/docs/tuna.8 b/docs/tuna.8
index dd69ec6..b6431be 100644
--- a/docs/tuna.8
+++ b/docs/tuna.8
@@ -65,6 +65,9 @@ CPU\-LIST affected by commands. Requires a CPU number or a comma-separated list
 \fB\-C\fR, \fB\-\-affect_children\fR
 Operation will affect children threads.
 .TP
+\fB\-d\fR, \fB\-\-disable_perf\fR
+Explicitly disable usage of perf in GUI for process view
+.TP
 \fB\-f\fR, \fB\-\-filter\fR
 Disable display of selected CPUs in \fB--gui\fR. Requires \fB-c\R.
 .TP
diff --git a/tuna-cmd.py b/tuna-cmd.py
index c27abd1..ecfa15e 100755
--- a/tuna-cmd.py
+++ b/tuna-cmd.py
@@ -59,6 +59,8 @@ def usage():
                  {"cpulist": _('CPU-LIST')}))
     print(fmt % ('-C, --affect_children',
                  _('Operation will affect children threads')))
+    print(fmt % ('-d, --disable_perf',
+                 _('Explicitly disable usage of perf in GUI for process view')))
     print(fmt % ('-f, --filter',
                  _('Display filter the selected entities')))
     print(fmt % ('-i, --isolate',               _('Move all threads away from %(cpulist)s') %
@@ -495,14 +497,14 @@ def main():
 
     i18n_init()
     try:
-        short = "a:c:CfgGhiIKlmNp:PQq:r:R:s:S:t:UvWx"
+        short = "a:c:dCfgGhiIKlmNp:PQq:r:R:s:S:t:UvWx"
         long = ["cpus=", "affect_children", "filter", "gui", "help",
                 "isolate", "include", "no_kthreads", "move", "nohz_full",
                 "show_sockets", "priority=", "show_threads",
                 "show_irqs", "irqs=",
                 "save=", "sockets=", "threads=", "no_uthreads",
                 "version", "what_is", "spread", "cgroup", "config_file_apply=",
-                "config_file_list=", "run=", "refresh="]
+                "config_file_list=", "run=", "refresh=", "disable_perf"]
         if have_inet_diag:
             short += "n"
             long.append("show_sockets")
@@ -528,6 +530,7 @@ def main():
     show_sockets = False
     p_waiting_action = False
     gui_refresh = 2500
+    disable_perf = False
 
     for o, a in opts:
         if o in ("-h", "--help"):
@@ -588,6 +591,9 @@ def main():
             except Exception as err:
                 print("tuna: --refresh %s" % err)
                 sys.exit(2)
+        elif o in ("-d", "--disable_perf"):
+            run_gui = True
+            disable_perf = True
         elif o in ("-i", "--isolate"):
             if not cpu_list:
                 print("tuna: --isolate " + _("requires a cpu list!"))
@@ -747,7 +753,7 @@ def main():
 
         try:
             cpus_filtered = filter and cpu_list or []
-            app = tuna_gui.main_gui(kthreads, uthreads, cpus_filtered, gui_refresh)
+            app = tuna_gui.main_gui(kthreads, uthreads, cpus_filtered, gui_refresh, disable_perf)
             app.run()
         except KeyboardInterrupt:
             pass
diff --git a/tuna/gui/procview.py b/tuna/gui/procview.py
index 28a73a3..440a289 100755
--- a/tuna/gui/procview.py
+++ b/tuna/gui/procview.py
@@ -214,7 +214,7 @@ class procview:
                gui.list_store_column(_("Command Line"), GObject.TYPE_STRING))
 
     def __init__(self, treeview, ps, show_kthreads, show_uthreads,
-                 cpus_filtered, gladefile):
+                 cpus_filtered, gladefile, disable_perf):
         self.ps = ps
         self.treeview = treeview
         self.nr_cpus = procfs.cpuinfo().nr_cpus
@@ -222,10 +222,11 @@ class procview:
         self.evlist_added = True
 
         self.evlist = None
-        try:
-            self.perf_init()
-        except: # No perf, poll /proc baby, poll
-            pass
+        if not disable_perf:
+            try:
+                self.perf_init()
+            except: # No perf, poll /proc baby, poll
+                pass
 
         if "voluntary_ctxt_switches" not in ps[1]["status"]:
             self.nr_columns = 5
diff --git a/tuna/tuna_gui.py b/tuna/tuna_gui.py
index ac50d93..f1f2caa 100755
--- a/tuna/tuna_gui.py
+++ b/tuna/tuna_gui.py
@@ -23,7 +23,7 @@ tuna_glade = None
 
 class main_gui:
 
-    def __init__(self, show_kthreads=True, show_uthreads=True, cpus_filtered=[], refresh_time=2500):
+    def __init__(self, show_kthreads=True, show_uthreads=True, cpus_filtered=[], refresh_time=2500, disable_perf=False):
         global tuna_glade
 
         (app, localedir) = ('tuna', '/usr/share/locale')
@@ -46,7 +46,7 @@ class main_gui:
         self.procview = procview(
             self.wtree.get_object("processlist"),
             self.ps, show_kthreads, show_uthreads,
-            cpus_filtered, tuna_glade)
+            cpus_filtered, tuna_glade, disable_perf)
         self.irqview = irqview(
             self.wtree.get_object("irqlist"),
             self.irqs, self.ps, cpus_filtered,