Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20181031' into staging

[qemu.git] / docs / devel / tracing.txt

diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 5768a0b7a2448690e310b07f0e28de1fb38eabbc..bc52f1248503cce9088a31c43ce1d208365ed6aa 100644 (file)
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -18,7 +18,7 @@ for debugging, profiling, and observing execution.
 
 3. Run the virtual machine to produce a trace file:
 
-    qemu -trace events=/tmp/events ... # your normal QEMU invocation
+    qemu --trace events=/tmp/events ... # your normal QEMU invocation
 
 4. Pretty-print the binary trace file:
 
@@ -104,6 +104,11 @@ Trace events should use types as follows:
  * For everything else, use primitive scalar types (char, int, long) with the
    appropriate signedness.
 
+ * Avoid floating point types (float and double) because SystemTap does not
+   support them.  In most cases it is possible to round to an integer type
+   instead.  This may require scaling the value first by multiplying it by 1000
+   or the like when digits after the decimal point need to be preserved.
+
 Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
 respectively.  This ensures portability between 32- and 64-bit platforms.
@@ -152,11 +157,11 @@ The state of events can also be queried and modified through monitor commands:
 * trace-event NAME on|off
   Enable/disable a given trace event or a group of events (using wildcards).
 
-The "-trace events=<file>" command line argument can be used to enable the
+The "--trace events=<file>" command line argument can be used to enable the
 events listed in <file> from the very beginning of the program. This file must
 contain one event name per line.
 
-If a line in the "-trace events=<file>" file begins with a '-', the trace event
+If a line in the "--trace events=<file>" file begins with a '-', the trace event
 will be disabled instead of enabled.  This is useful when a wildcard was used
 to enable an entire family of events but one noisy event needs to be disabled.
 
@@ -353,7 +358,7 @@ guard such computations and avoid its compilation when the event is disabled:
     }
 
 You can check both if the event has been disabled and is dynamically enabled at
-the same time using the 'trace_event_get_state' routine (see header
+the same time using the 'trace_event_get_state_backends' routine (see header
 "trace/control.h" for more information).
 
 === "tcg" ===