docs: Update stderr and simple backend, add systemtap backend
The following additions to the tracing documentation are included: 1. Move "stderr" backend documentation to top-level and out of "simple" backend. Include hints on when this backend is useful. 2. Document the "simple" backend thread-safety limitation. 3. Document the "dtrace" backend for SystemTap. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
parent
59da668492
commit
b48c20f723
|
@ -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
|
can optimize out trace events completely. This is the default and imposes no
|
||||||
performance penalty.
|
performance penalty.
|
||||||
|
|
||||||
|
=== 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
|
||||||
|
uses DPRINTF().
|
||||||
|
|
||||||
=== Simpletrace ===
|
=== Simpletrace ===
|
||||||
|
|
||||||
The "simple" backend supports common use cases and comes as part of the QEMU
|
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
|
trace backends but it is portable. This is the recommended trace backend
|
||||||
unless you have specific needs for more advanced backends.
|
unless you have specific needs for more advanced backends.
|
||||||
|
|
||||||
=== Stderr ===
|
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
|
||||||
The "stderr" backend sends trace events directly to standard error output
|
requirement but some utility functions like qemu_malloc() or thread-related
|
||||||
during emulation.
|
code cannot be safely traced using the "simple" backend.
|
||||||
|
|
||||||
==== Monitor commands ====
|
==== Monitor commands ====
|
||||||
|
|
||||||
|
@ -187,3 +195,17 @@ consistent.
|
||||||
The "ust" backend uses the LTTng Userspace Tracer library. There are no
|
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,
|
monitor commands built into QEMU, instead UST utilities should be used to list,
|
||||||
enable/disable, and dump traces.
|
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
|
||||||
|
probes:
|
||||||
|
|
||||||
|
scripts/tracetool --dtrace --stap \
|
||||||
|
--binary path/to/qemu-binary \
|
||||||
|
--target-type system \
|
||||||
|
--target-arch x86_64 \
|
||||||
|
<trace-events >qemu.stp
|
||||||
|
|
Loading…
Reference in New Issue