Re: [Qemu-devel] [PATCH v4 ] trace: Multi-backend tracing

[Lluís Vilanova]

Stefan Hajnoczi writes:

> On Tue, May 13, 2014 at 08:04:13PM +0200, Lluís Vilanova wrote:
>> Adds support to compile QEMU with multiple tracing backends at the same time.
>> 
>> For example, you can compile QEMU with:
>> 
>> $ ./configure --enable-trace-backends=ftrace,dtrace
>> 
>> Where 'ftrace' can be handy for having an in-flight record of events, and 
>> 'dtrace' can be later used to extract more information from the system.
>> 
>> This patch allows having both available without recompiling QEMU.
>> 
>> Signed-off-by: Lluís Vilanova <address@hidden>
>> ---
>> .travis.yml                           |    8 +++--
>> Makefile                              |    4 +--
>> Makefile.target                       |    4 +--
>> configure                             |   44 +++++++++++++-----------------
>> docs/tracing.txt                      |    4 +--
>> qemu-io.c                             |    2 +
>> scripts/tracetool.py                  |   41 ++++++++++++++--------------
>> scripts/tracetool/__init__.py         |   24 +++++++---------
>> scripts/tracetool/backend/__init__.py |   15 +++++-----
>> trace/Makefile.objs                   |   22 +++++++--------
>> trace/control-internal.h              |    4 +--
>> trace/control.c                       |   49 
>> ++++++++++++++++++++++++++++++++-
>> trace/control.h                       |   27 +++---------------
>> trace/default.c                       |   40 ---------------------------
>> trace/ftrace.c                        |   25 +----------------
>> trace/ftrace.h                        |    5 +++
>> trace/simple.c                        |   19 +------------
>> trace/simple.h                        |    1 +
>> trace/stderr.c                        |   30 --------------------
>> vl.c                                  |    4 +--
>> 20 files changed, 144 insertions(+), 228 deletions(-)
>> delete mode 100644 trace/default.c
>> delete mode 100644 trace/stderr.c

> This doesn't seem to work 100% yet:

> $ ./configure --target-list=x86_64-softmmu 
> --enable-trace-backends=dtrace,simple && make
> ...
> lt LINK vscclient
> ./.libs/libcacard.so: undefined reference to
> `_simple_trace_qemu_anon_ram_alloc'
> ./.libs/libcacard.so: undefined reference to
> `_simple_trace_qemu_anon_ram_free'
> ./.libs/libcacard.so: undefined reference to `_simple_trace_qemu_vfree'
> ./.libs/libcacard.so: undefined reference to
> `_simple_trace_qemu_memalign'

Silly mistake, I didn't try building with dtrace.


> I also noticed that ./configure invokes tracetool.py with the old
> --enable-trace-backend option after applying the patch.  The build
> succeeds but the tracetool.py usage is printed.

> This is because ./configure stores the command-line in config.status and
> reruns itself if config-host.mak needs to be rebuilt.  It's using the
> old ./configure command-line that was stashed in config.status.

> The good news is this shouldn't affect buildbot but it will probably
> surprise all the developers who git pull qemu.git and then see an error
> message from ./configure.

> Since you are respinning, please consider a fix for this.  Perhaps we
> can accept the old command-line argument but not document it.

Done.


>> @@ -65,16 +65,17 @@ def main(args):
>> global _SCRIPT
>> _SCRIPT = args[0]
>> 
>> -    long_opts  = [ "backend=", "format=", "help", "list-backends", 
>> "check-backend" ]
>> -    long_opts += [ "binary=", "target-type=", "target-name=", 
>> "probe-prefix=" ]
>> +    long_opts = ["backends=", "format=", "help", "list-backends",
>> +                 "check-backends"]
>> +    long_opts += ["binary=", "target-type=", "target-name=", 
>> "probe-prefix="]

> Missing tracetool.py help output s/--check-backend/--check-backends/.

Done.

I'll send v5 now.


Thanks,
  Lluis

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