[Qemu-devel] [PATCH v5 5/7] trace: Conditionally trace events based on their per-vCPU state

[Lluís Vilanova]

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 <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
 scripts/tracetool/backend/dtrace.py |    4 ++--
 scripts/tracetool/backend/ftrace.py |   20 ++++++++++----------
 scripts/tracetool/backend/log.py    |   26 ++++++++++++++++----------
 scripts/tracetool/backend/simple.py |   13 ++++++++++---
 scripts/tracetool/backend/ust.py    |    4 ++--
 scripts/tracetool/format/h.py       |   18 ++++++++++++++++--
 6 files changed, 56 insertions(+), 29 deletions(-)

diff --git a/scripts/tracetool/backend/dtrace.py 
b/scripts/tracetool/backend/dtrace.py
index fabfe99..ab9ecfa 100644
--- a/scripts/tracetool/backend/dtrace.py
+++ b/scripts/tracetool/backend/dtrace.py
@@ -6,7 +6,7 @@ DTrace/SystemTAP backend.
 """
 
 __author__     = "Lluís Vilanova <address@hidden>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <address@hidden>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <address@hidden>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -41,6 +41,6 @@ def generate_h_begin(events):
 
 
 def generate_h(event):
-    out('    QEMU_%(uppername)s(%(argnames)s);',
+    out('        QEMU_%(uppername)s(%(argnames)s);',
         uppername=event.name.upper(),
         argnames=", ".join(event.args.names()))
diff --git a/scripts/tracetool/backend/ftrace.py 
b/scripts/tracetool/backend/ftrace.py
index d798c71..80dcf30 100644
--- a/scripts/tracetool/backend/ftrace.py
+++ b/scripts/tracetool/backend/ftrace.py
@@ -30,17 +30,17 @@ def generate_h(event):
     if len(event.args) > 0:
         argnames = ", " + argnames
 
-    out('    {',
-        '        char ftrace_buf[MAX_TRACE_STRLEN];',
-        '        int unused __attribute__ ((unused));',
-        '        int trlen;',
-        '        if (trace_event_get_state(%(event_id)s)) {',
-        '            trlen = snprintf(ftrace_buf, MAX_TRACE_STRLEN,',
-        '                             "%(name)s " %(fmt)s "\\n" 
%(argnames)s);',
-        '            trlen = MIN(trlen, MAX_TRACE_STRLEN - 1);',
-        '            unused = write(trace_marker_fd, ftrace_buf, trlen);',
+    out('        {',
+        '            char ftrace_buf[MAX_TRACE_STRLEN];',
+        '            int unused __attribute__ ((unused));',
+        '            int trlen;',
+        '            if (trace_event_get_state(%(event_id)s)) {',
+        '                trlen = snprintf(ftrace_buf, MAX_TRACE_STRLEN,',
+        '                                 "%(name)s " %(fmt)s "\\n" 
%(argnames)s);',
+        '                trlen = MIN(trlen, MAX_TRACE_STRLEN - 1);',
+        '                unused = write(trace_marker_fd, ftrace_buf, trlen);',
+        '            }',
         '        }',
-        '    }',
         name=event.name,
         args=event.args,
         event_id="TRACE_" + event.name.upper(),
diff --git a/scripts/tracetool/backend/log.py b/scripts/tracetool/backend/log.py
index e409b73..b3ff064 100644
--- a/scripts/tracetool/backend/log.py
+++ b/scripts/tracetool/backend/log.py
@@ -6,7 +6,7 @@ Stderr built-in backend.
 """
 
 __author__     = "Lluís Vilanova <address@hidden>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <address@hidden>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <address@hidden>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -30,15 +30,21 @@ def generate_h(event):
     if len(event.args) > 0:
         argnames = ", " + argnames
 
-    out('    if (trace_event_get_state(%(event_id)s)) {',
-        '        struct timeval _now;',
-        '        gettimeofday(&_now, NULL);',
-        '        qemu_log_mask(LOG_TRACE, "address@hidden:%(name)s " %(fmt)s 
"\\n",',
-        '                      getpid(),',
-        '                      (size_t)_now.tv_sec, (size_t)_now.tv_usec',
-        '                      %(argnames)s);',
-        '    }',
-        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)" % ("TRACE_" + event.name.upper())
+
+    out('        if (%(cond)s) {',
+        '            struct timeval _now;',
+        '            gettimeofday(&_now, NULL);',
+        '            qemu_log_mask(LOG_TRACE, "address@hidden:%(name)s " 
%(fmt)s "\\n",',
+        '                          getpid(),',
+        '                          (size_t)_now.tv_sec, (size_t)_now.tv_usec',
+        '                          %(argnames)s);',
+        '        }',
+        cond=cond,
         name=event.name,
         fmt=event.fmt.rstrip("\n"),
         argnames=argnames)
diff --git a/scripts/tracetool/backend/simple.py 
b/scripts/tracetool/backend/simple.py
index 3246c20..1bccada 100644
--- a/scripts/tracetool/backend/simple.py
+++ b/scripts/tracetool/backend/simple.py
@@ -36,7 +36,7 @@ def generate_h_begin(events):
 
 
 def generate_h(event):
-    out('    _simple_%(api)s(%(args)s);',
+    out('        _simple_%(api)s(%(args)s);',
         api=event.api(),
         args=", ".join(event.args.names()))
 
@@ -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:
diff --git a/scripts/tracetool/backend/ust.py b/scripts/tracetool/backend/ust.py
index 2f8f44a..ed4c227 100644
--- a/scripts/tracetool/backend/ust.py
+++ b/scripts/tracetool/backend/ust.py
@@ -6,7 +6,7 @@ LTTng User Space Tracing backend.
 """
 
 __author__     = "Lluís Vilanova <address@hidden>"
-__copyright__  = "Copyright 2012-2014, Lluís Vilanova <address@hidden>"
+__copyright__  = "Copyright 2012-2016, Lluís Vilanova <address@hidden>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -30,6 +30,6 @@ def generate_h(event):
     if len(event.args) > 0:
         argnames = ", " + argnames
 
-    out('    tracepoint(qemu, %(name)s%(tp_args)s);',
+    out('        tracepoint(qemu, %(name)s%(tp_args)s);',
         name=event.name,
         tp_args=argnames)
diff --git a/scripts/tracetool/format/h.py b/scripts/tracetool/format/h.py
index 0835406..f4311fd 100644
--- a/scripts/tracetool/format/h.py
+++ b/scripts/tracetool/format/h.py
@@ -28,16 +28,30 @@ def generate(events, backend):
     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)