Re: [Qemu-devel] [PATCH v2] trace: Clarify DTrace/SystemTap help message

[Stefan Hajnoczi]

On Fri, Aug 23, 2019 at 04:22:03PM +0200, Philippe Mathieu-Daudé wrote:
> Most tracing backends are implemented within QEMU, except the
> DTrace/SystemTap backends.
> 
> One side effect is when running 'qemu -trace help', an incomplete
> list of trace events is displayed when using the DTrace/SystemTap
> backends.
> 
> This is partly due to trace events registered as modules with
> trace_init(), and since the events are not used within QEMU,
> the linker optimize and remove the unused modules (which is
> OK in this particular case).
> Currently only the events compiled in trace-root.o and in the
> last trace.o member of libqemuutil.a are linked, resulting in
> an incomplete list of events.
> 
> To avoid confusion, improve the help message, recommending to
> use the proper systemtap script to display the events list.
> 
> Before:
> 
>   $ lm32-softmmu/qemu-system-lm32 -trace help 2>&1 | wc -l
>   70
> 
> After:
> 
>   $ lm32-softmmu/qemu-system-lm32 -trace help
>   Run 'qemu-trace-stap list qemu-system-lm32' to print a list
>   of names of trace points with the DTrace/SystemTap backends.
> 
>   $ qemu-trace-stap list qemu-system-lm32 | wc -l
>   1136
> 
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> v2: Consider when multiple trace backends are used (Stefan)
> ---
>  trace/control.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Thanks, applied to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing

Stefan

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