SYS-OSS/FRET-qemu
4
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

docs: Update stderr and simple backend, add systemtap backend

Browse Source 
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:
Stefan Hajnoczi 2011-02-23 14:00:21 +00:00 committed by Aurelien Jarno
parent 59da668492
commit b48c20f723
1 changed files with 26 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
docs/tracing.txt
View File

@ -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
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 ===
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
during emulation.
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
probes:
scripts/tracetool --dtrace --stap \
--binary path/to/qemu-binary \
--target-type system \
--target-arch x86_64 \
<trace-events >qemu.stp