trace: Conditionally trace events based on their per-vCPU state

Events with the 'vcpu' property are conditionally emitted according to
their per-vCPU state. Other events are emitted normally based on their
global tracing state.

Note that the per-vCPU condition check applies to all tracing backends.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/tracetool/backend/dtrace.py

@@ -6,7 +6,7 @@ DTrace/SystemTAP backend.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"

scripts/tracetool/backend/log.py

@@ -6,7 +6,7 @@ Stderr built-in backend.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -30,7 +30,13 @@ def generate_h(event):
     if len(event.args) > 0:
         argnames = ", " + argnames
 
-    out('    if (trace_event_get_state(%(event_id)s)) {',
+    if "vcpu" in event.properties:
+        # already checked on the generic format code
+        cond = "true"
+    else:
+        cond = "trace_event_get_state(%s)" % ("TRACE_" + event.name.upper())
+
+    out('        if (%(cond)s) {',
         '            struct timeval _now;',
         '            gettimeofday(&_now, NULL);',
         '            qemu_log_mask(LOG_TRACE, "%%d@%%zd.%%06zd:%(name)s " %(fmt)s "\\n",',
@@ -38,7 +44,7 @@ def generate_h(event):
         '                          (size_t)_now.tv_sec, (size_t)_now.tv_usec',
         '                          %(argnames)s);',
         '        }',
-        event_id="TRACE_" + event.name.upper(),
+        cond=cond,
         name=event.name,
         fmt=event.fmt.rstrip("\n"),
         argnames=argnames)

scripts/tracetool/backend/simple.py

@@ -68,16 +68,23 @@ def generate_c(event):
     if len(event.args) == 0:
         sizestr = '0'
 
+    event_id = 'TRACE_' + event.name.upper()
+    if "vcpu" in event.properties:
+        # already checked on the generic format code
+        cond = "true"
+    else:
+        cond = "trace_event_get_state(%s)" % event_id
 
     out('',
-        '    if (!trace_event_get_state(%(event_id)s)) {',
+        '    if (!%(cond)s) {',
         '        return;',
         '    }',
         '',
         '    if (trace_record_start(&rec, %(event_id)s, %(size_str)s)) {',
         '        return; /* Trace Buffer Full, Event Dropped ! */',
         '    }',
-        event_id='TRACE_' + event.name.upper(),
+        cond=cond,
+        event_id=event_id,
         size_str=sizestr)
 
     if len(event.args) > 0:

scripts/tracetool/backend/ust.py

@@ -6,7 +6,7 @@ LTTng User Space Tracing backend.
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"

scripts/tracetool/format/h.py

@@ -23,21 +23,36 @@ def generate(events, backend):
         '#define TRACE__GENERATED_TRACERS_H',
         '',
         '#include "qemu-common.h"',
+        '#include "trace/control.h"',
         '')
 
     backend.generate_begin(events)
 
     for e in events:
+        if "vcpu" in e.properties:
+            trace_cpu = next(iter(e.args))[1]
+            cond = "trace_event_get_vcpu_state(%(cpu)s,"\
+                   " TRACE_%(id)s,"\
+                   " TRACE_VCPU_%(id)s)"\
+                   % dict(
+                       cpu=trace_cpu,
+                       id=e.name.upper())
+        else:
+            cond = "true"
+
         out('',
             'static inline void %(api)s(%(args)s)',
             '{',
+            '    if (%(cond)s) {',
             api=e.api(),
-            args=e.args)
+            args=e.args,
+            cond=cond)
 
         if "disable" not in e.properties:
             backend.generate(e)
 
-        out('}')
+        out('    }',
+            '}')
 
     backend.generate_end(events)