trace: [tcg] Do not generate TCG code to trace dynamically-disabled events

If an event is dynamically disabled, the TCG code that calls the
execution-time tracer is not generated.

Removes the overheads of execution-time tracers for dynamically disabled
events. As a bonus, also avoids checking the event state when the
execution-time tracer is called from TCG-generated code (since otherwise
TCG would simply not call it).

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-id: 149915799921.6295.13067154430923434035.stgit@frigg.lan
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/tracetool/__init__.py

@@ -6,7 +6,7 @@ Machinery for generating tracing-related intermediate files.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2017, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -268,6 +268,7 @@ class Event(object):
         return self._FMT.findall(self.fmt)
 
     QEMU_TRACE               = "trace_%(name)s"
+    QEMU_TRACE_NOCHECK       = "_nocheck__" + QEMU_TRACE
     QEMU_TRACE_TCG           = QEMU_TRACE + "_tcg"
     QEMU_DSTATE              = "_TRACE_%(NAME)s_DSTATE"
     QEMU_EVENT               = "_TRACE_%(NAME)s_EVENT"

scripts/tracetool/format/h.py

@@ -6,7 +6,7 @@ trace/generated-tracers.h
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2017, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -49,6 +49,19 @@ def generate(events, backend, group):
     backend.generate_begin(events, group)
 
     for e in events:
+        # tracer without checks
+        out('',
+            'static inline void %(api)s(%(args)s)',
+            '{',
+            api=e.api(e.QEMU_TRACE_NOCHECK),
+            args=e.args)
+
+        if "disable" not in e.properties:
+            backend.generate(e, group)
+
+        out('}')
+
+        # tracer wrapper with checks (per-vCPU tracing)
         if "vcpu" in e.properties:
             trace_cpu = next(iter(e.args))[1]
             cond = "trace_event_get_vcpu_state(%(cpu)s,"\
@@ -63,16 +76,15 @@ def generate(events, backend, group):
             'static inline void %(api)s(%(args)s)',
             '{',
             '    if (%(cond)s) {',
+            '        %(api_nocheck)s(%(names)s);',
+            '    }',
+            '}',
             api=e.api(),
+            api_nocheck=e.api(e.QEMU_TRACE_NOCHECK),
             args=e.args,
+            names=", ".join(e.args.names()),
             cond=cond)
 
-        if "disable" not in e.properties:
-            backend.generate(e, group)
-
-        out('    }',
-            '}')
-
     backend.generate_end(events, group)
 
     out('#endif /* TRACE_%s_GENERATED_TRACERS_H */' % group.upper())

scripts/tracetool/format/tcg_h.py

@@ -6,7 +6,7 @@ Generate .h file for TCG code generation.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2017, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -46,7 +46,7 @@ def generate(events, backend, group):
 
     for e in events:
         # just keep one of them
-        if "tcg-trans" not in e.properties:
+        if "tcg-exec" not in e.properties:
             continue
 
         out('static inline void %(name_tcg)s(%(args)s)',
@@ -58,12 +58,25 @@ def generate(events, backend, group):
             args_trans = e.original.event_trans.args
             args_exec = tracetool.vcpu.transform_args(
                 "tcg_helper_c", e.original.event_exec, "wrapper")
+            if "vcpu" in e.properties:
+                trace_cpu = e.args.names()[0]
+                cond = "trace_event_get_vcpu_state(%(cpu)s,"\
+                       " TRACE_%(id)s)"\
+                       % dict(
+                           cpu=trace_cpu,
+                           id=e.original.event_exec.name.upper())
+            else:
+                cond = "true"
+
             out('    %(name_trans)s(%(argnames_trans)s);',
-                '    gen_helper_%(name_exec)s(%(argnames_exec)s);',
+                '    if (%(cond)s) {',
+                '        gen_helper_%(name_exec)s(%(argnames_exec)s);',
+                '    }',
                 name_trans=e.original.event_trans.api(e.QEMU_TRACE),
                 name_exec=e.original.event_exec.api(e.QEMU_TRACE),
                 argnames_trans=", ".join(args_trans.names()),
-                argnames_exec=", ".join(args_exec.names()))
+                argnames_exec=", ".join(args_exec.names()),
+                cond=cond)
 
         out('}')
 

scripts/tracetool/format/tcg_helper_c.py

@@ -6,7 +6,7 @@ Generate trace/generated-helpers.c.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2017, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -71,10 +71,11 @@ def generate(events, backend, group):
 
         out('void %(name_tcg)s(%(args_api)s)',
             '{',
+            # NOTE: the check was already performed at TCG-generation time
             '    %(name)s(%(args_call)s);',
             '}',
             name_tcg="helper_%s_proxy" % e.api(),
-            name=e.api(),
+            name=e.api(e.QEMU_TRACE_NOCHECK),
             args_api=e_args_api,
             args_call=", ".join(e_args_call.casted()),
             )