This is the mail archive of the
systemtap@sourceware.org
mailing list for the systemtap project.
Re: LTTng-UST vs SystemTap userspace tracing benchmarks
- From: Julien Desfossez <julien dot desfossez at polymtl dot ca>
- To: Tom Tromey <tromey at redhat dot com>
- Cc: ltt-dev at lists dot casi dot polymtl dot ca, systemtap at sources dot redhat dot com, Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>, dominique dot toupin at ericsson dot com
- Date: Thu, 17 Feb 2011 12:33:35 -0500
- Subject: Re: LTTng-UST vs SystemTap userspace tracing benchmarks
- References: <4D5AA164.1050607@polymtl.ca> <m37hd06lpj.fsf@fleche.redhat.com>
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