[Qemu-devel] [PATCH v5 5/7] trace: [tcg] Do not generate TCG code to trace dinamically-disabled events

[Lluís Vilanova]

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 <address@hidden>
---
 scripts/tracetool/__init__.py            |    1 +
 scripts/tracetool/format/h.py            |   24 ++++++++++++++++++------
 scripts/tracetool/format/tcg_h.py        |   19 ++++++++++++++++---
 scripts/tracetool/format/tcg_helper_c.py |    3 ++-
 4 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 365446fa53..63168ccdf0 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -264,6 +264,7 @@ 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"
diff --git a/scripts/tracetool/format/h.py b/scripts/tracetool/format/h.py
index 3682f4e6a8..a78e50ef35 100644
--- a/scripts/tracetool/format/h.py
+++ b/scripts/tracetool/format/h.py
@@ -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())
diff --git a/scripts/tracetool/format/tcg_h.py 
b/scripts/tracetool/format/tcg_h.py
index 5f213f6cba..71b5c09432 100644
--- a/scripts/tracetool/format/tcg_h.py
+++ b/scripts/tracetool/format/tcg_h.py
@@ -41,7 +41,7 @@ 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)',
@@ -53,12 +53,25 @@ 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('}')
 
diff --git a/scripts/tracetool/format/tcg_helper_c.py 
b/scripts/tracetool/format/tcg_helper_c.py
index cc26e03008..c2a05d756c 100644
--- a/scripts/tracetool/format/tcg_helper_c.py
+++ b/scripts/tracetool/format/tcg_helper_c.py
@@ -66,10 +66,11 @@ 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()),
             )