dtrace discuss - Jul 2010 - condition probe argument construction in static probes

Hi,

is it somehow possible to conditionally enable a section of code that is
responsible for constructing a probe argument.

I.e. if the first probe argument is a string, can I attach a function to the
probe that will yield that string so that it doesn''t have to be
constructed if the probe doesn''t fire?

Defining the following probe yields assembly that executes the call to
expensive_argument_construction unconditionally...

DTRACE_PROBE1(myprovider,myprobe,expensive_argument_construction());

- Thomas
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This message posted from opensolaris.org

I think you''re looking for is-enabled probes.  See
http://blogs.sun.com/ahl/entry/user_land_tracing_gets_better or the
current DTrace documentation.

Chad

On Fri, Jul 16, 2010 at 10:39 AM, Thomas Maier-Komor
<thomas at maier-komor.de> wrote:
> Hi,
>
> is it somehow possible to conditionally enable a section of code that is
responsible for constructing a probe argument.
>
> I.e. if the first probe argument is a string, can I attach a function to
the probe that will yield that string so that it doesn''t have to be
constructed if the probe doesn''t fire?
>
> Defining the following probe yields assembly that executes the call to
expensive_argument_construction unconditionally...
>
> DTRACE_PROBE1(myprovider,myprobe,expensive_argument_construction());
>
> - Thomas
> --
> This message posted from opensolaris.org
> _______________________________________________
> dtrace-discuss mailing list
> dtrace-discuss at opensolaris.org
>

replying to myself...

dtrace -h and <provider>_<probe>_ENABLED() seems to be the clue

This still yields a clear register -> nops -> jump-conditionally assembler
sequence. But this is almost zero overhead...

Or is there anything better?

- Thomas
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This message posted from opensolaris.org

yes, that is what I was looking for and what I found myself before reading your
e-mail. Your answer just came unexpectedly quick.

Thanks anyway!

Cheers,
Thomas
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This message posted from opensolaris.org