Re: [Qemu-devel] [PATCH v2] Add a DTrace tracing backend targetted for SystemTAP compatability

[Prerna Saxena]

ACK, works well!
A suggestion though..

On 10/20/2010 07:39 PM, Daniel P. Berrange wrote:
> eg, instead of
>
>    probe process("qemu").mark("qemu_malloc") {
>      printf("Malloc %d %p\n", $arg1, $arg2);
>    }
>
> The addition of qemu.stp to /usr/share/systemtap/tapset/
> lets users write
>
>    probe qemu.qemu_malloc {
>      printf("Malloc %d %p\n", size, ptr);
>    }
> ...
>
>
> diff --git a/tracetool b/tracetool
> index 7010858..047f16b 100755
> --- a/tracetool
> +++ b/tracetool
> +linetos_dtrace()
> +{
> +    local name args arglist state
> +
> +    # Define prototype for probe arguments
> +    cat<<EOF
> +probe qemu.$name = process("qemu").mark("$name")
> +{

The 'process' probes only work by looking for the binary in $PATH, 
unless the full path is specified. When compiling qemu in non-standard 
locations ( ie with --prefix), such probes would not point to the 
correct binary. It could be nice if tracetool could pass the full build 
path for defining the probe point. Eg,

probe qemu.qemu_malloc = 
process("/Path/to/build/dir/bin/qemu").mark("qemu_malloc") { .. }

--
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India