[Qemu-devel] [Tracing][PATCH] Allow bulk enabling of trace events at compile time.

[Prerna Saxena <prerna@linux.vnet.ibm.com>]

[PATCH] For 'simple' trace backend, allow bulk enabling/disabling of trace
 events at compile time.
 Trace events that are preceded by 'disable' keyword are compiled in, but 
 turned off by default. These can individually be turned on using the monitor.
 All other trace events are enabled by default.

TODO :
This could be enhanced when the trace-event namespace is partitioned into a
group and an ID within that group. In such a case, marking a group as enabled 
would automatically enable all trace-events listed under it.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---
 trace-events |    3 +++
 tracetool    |   36 ++++++++++++++++++++++++++++++++----
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/trace-events b/trace-events
index a533414..cb5ef00 100644
--- a/trace-events
+++ b/trace-events
@@ -17,6 +17,9 @@
 # Example: qemu_malloc(size_t size) "size %zu"
 #
 # The "disable" keyword will build without the trace event.
+# In case of 'simple' trace backend, it will allow the trace event to be
+# compiled, but this would be turned off by default. It can be toggled on via 
+# the monitor.
 #
 # The <name> must be a valid as a C function name.
 #
diff --git a/tracetool b/tracetool
index b7a0499..98d23fb 100755
--- a/tracetool
+++ b/tracetool
@@ -73,6 +73,20 @@ get_fmt()
     echo "$fmt"
 }
 
+# Get the state of a trace event
+get_state()
+{
+    local str disable state
+    str=$(get_name "$1")
+    disable=${str##disable }
+    if [ "$disable" = "$str" ] ; then
+        state=1
+    else
+        state=0
+    fi
+    echo "$state"
+}
+
 linetoh_begin_nop()
 {
     return
@@ -155,12 +169,16 @@ cast_args_to_ulong()
 
 linetoh_simple()
 {
-    local name args argc ulong_args
+    local name args argc ulong_args state
     name=$(get_name "$1")
     args=$(get_args "$1")
     argc=$(get_argc "$1")
     ulong_args=$(cast_args_to_ulong "$1")
 
+    state=$(get_state "$1")
+    if [ "$state" = "0" ]; then
+        name=${name##disable }
+    fi
     cat <<EOF
 static inline void trace_$name($args) {
     trace$argc($simple_event_num, $ulong_args);
@@ -191,10 +209,14 @@ EOF
 
 linetoc_simple()
 {
-    local name
+    local name state
     name=$(get_name "$1")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
     cat <<EOF
-{.tp_name = "$name", .state=0},
+{.tp_name = "$name", .state=$state},
 EOF
     simple_event_num=$((simple_event_num + 1))
 }
@@ -305,7 +327,13 @@ convert()
         disable=${str%%disable *}
         echo
         if test -z "$disable"; then
-            "lineto$1_nop" "${str##disable }"
+            # Pass the disabled state as an arg to lineto$1_simple().
+            # For all other cases, call lineto$1_nop()
+            if [ $backend = "simple" ]; then
+                "$process_line" "$str"
+            else
+                "lineto$1_nop" "${str##disable }"
+            fi
         else
             "$process_line" "$str"
         fi
-- 
1.6.2.5



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India