@@ -126,6 +126,14 @@ The "nop" backend generates empty trace event functions so that the compiler
can optimize out trace events completely. This is the default and imposes no
+=== Stderr ===
+The "stderr" backend sends trace events directly to standard error. This
+effectively turns trace events into debug printfs.
+This is the simplest backend and can be used together with existing code that
=== Simpletrace ===
The "simple" backend supports common use cases and comes as part of the QEMU
@@ -133,10 +141,10 @@ source tree. It may not be as powerful as platform-specific or third-party
trace backends but it is portable. This is the recommended trace backend
unless you have specific needs for more advanced backends.
-=== Stderr ===
-The "stderr" backend sends trace events directly to standard error output
+Warning: the "simple" backend is not thread-safe so only enable trace events
+that are executed while the global mutex is held. Much of QEMU meets this
+requirement but some utility functions like qemu_malloc() or thread-related
+code cannot be safely traced using the "simple" backend.
==== Monitor commands ====
@@ -187,3 +195,17 @@ consistent.
The "ust" backend uses the LTTng Userspace Tracer library. There are no
monitor commands built into QEMU, instead UST utilities should be used to list,
enable/disable, and dump traces.
+=== SystemTap ===
+The "dtrace" backend uses DTrace sdt probes but has only been tested with
+SystemTap. When SystemTap support is detected a .stp file with wrapper probes
+is generated to make use in scripts more convenient. This step can also be
+performed manually after a build in order to change the binary name in the .stp
+ scripts/tracetool --dtrace --stap \
+ --binary path/to/qemu-binary \
+ --target-type system \
+ --target-arch x86_64 \
+ <trace-events >qemu.stp