[php-maint] Bug#730528: Bug#730528: Enable dtrace/systemtap support

Vincent Bernat bernat at debian.org
Fri Dec 6 11:53:28 UTC 2013

 ❦  6 décembre 2013 10:05 CET, Ondřej Surý <ondrej at sury.org> :

> could you please elaborate more?  What benefits would that have to
> general users and is there any performance (or any other) drawbacks in
> enabling this?

Such a support allows a user to answers questions like:

 - how many time do we hit this function?
 - how long a request whose URI starts with /api takes?
 - is this function still used?
 - what is the repartition of request times for my webserver?

And all this on production systems with a very low overhead.

When the user is not using tracing at all, there is zero impact on
performance because it expands to a NOP instruction. Only when a user is
requesting to put a probe in action, the NOP will be turned into an
appropriate instruction to be trapped by the kernel. See:

Make sure comments and code agree.
            - The Elements of Programming Style (Kernighan & Plauger)
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