[ltt-dev] LTTng-UST vs SystemTap userspace tracing benchmarks

[Julien Desfossez]

Hi,

On 02/16/2011 10:30 AM, Tom Tromey wrote:
> Julien> 0) Baseline : running the program without any instrumentation
> Julien> 1) Flight recorder tracing comparison UST vs SystemTap
> 
> I'd be interested to also see the numbers when the probes are in place
> in the source, but not enabled.  That is, what is the overhead of a
> disabled probe?
I disabled the probe by undefining HAVE_SYSTEMTAP, but I have the same
results in flight recorder mode. Of course if the module is not loaded
we have no overhead at all. It means that the module is responsible for
all the overhead regarless if the probe is called or not.
I would be really interested if you know why it happens (and how to fix it).
This last test was done on a Fedora Core 14 (kernel
2.6.35.10-74.fc14.x86_64 with SystemTap 1.3-3).

If you want to test, the benchmark code is here :
git://git.lttng.org/benchmarks.git

Thanks,

Julien