Re: Tips regarding measuring function execution times

[Roland Knall <rknall () gmail com>]

Please keep in mind, that those are not very precise. High-resolution timer
measurements cannot be done in a precise fashion on most windows systems
for ethernet applications. You would need to take the time immediately in
the MAC receiving the packet, everything above is already adding delays in
the time measurement. For exact that reason, most equipment for error
analysis in Industrial Ethernet systems (which rely heavily on precise
nano- and microsecond timestamps) use external (FPGA-based) hardware to
create the trace and 3rd party utilities to provide them to Wireshark.

In other words, microseconds is as reliable as it gets.

On Mon, Oct 16, 2017 at 8:34 AM, Paul Offord <Paul.Offord () advance7 com>
wrote:

> Hi Roland,
>
>
>
> I’m only doing this for debugging purposes, and I accumulate the total
> time as each packet is dissected.  To get the value as output I’ve put the
> printf in a cleanup routine that gets triggered when I close the trace file.
>
>
>
> Unfortunately, microsecond granularity is not going to do it.  All start
> and end times produced by the code below are equal – giving an elapsed time
> of zero.  I’ve been looking at Windows nanosecond timers but I’ll have to
> use C++ to get access to those.
>
>
>
> Best regards….Paul
>
>
>
> *From:* Wireshark-dev [mailto:wireshark-dev-bounces () wireshark org] *On
> Behalf Of *Roland Knall
> *Sent:* 16 October 2017 05:38
>
> *To:* Developer support list for Wireshark <wireshark-dev () wireshark org>
> *Subject:* Re: [Wireshark-dev] Tips regarding measuring function
> execution times
>
>
>
> Keep in mind, that printf is by far one of the slowest functions.
> Additionally it slows also down the output as well. I'd recommend writing
> the times into a buffer and dumping them in intervalls, very much like the
> tap's work, otherwise what you see might not be what is happening on the
> network.
>
>
>
> cheers
>
>
>
> On Sun, Oct 15, 2017 at 11:15 PM, Paul Offord <Paul.Offord () advance7 com>
> wrote:
>
> Thanks to all for the tips.  I’ll give it a go.
>
>
>
> *From:* Wireshark-dev [mailto:wireshark-dev-bounces () wireshark org] *On
> Behalf Of *Pascal Quantin
> *Sent:* 15 October 2017 21:50
> *To:* Developer support list for Wireshark <wireshark-dev () wireshark org>
> *Subject:* Re: [Wireshark-dev] Tips regarding measuring function
> execution times
>
>
>
>
>
>
>
> 2017-10-15 22:40 GMT+02:00 João Valverde <joao.valverde () tecnico ulisboa pt
> > :
>
>
>
> On 15-10-2017 21:32, Peter Wu wrote:
>
> On Sat, Oct 14, 2017 at 02:18:39PM +0000, Paul Offord wrote:
>
> I'm investigating a performance problem with the TRANSUM dissector.  I'd
> like to measure the accumulated time taken to execute a function in a
> Release build.  My basic idea is to do something like this:
>
> guint32 execute_time_us;
> .
> .
> start_stopwatch(&execute_time_us);
> function_call_to_be_measured();
> pause_stopwatch(&execute_time_us);
>
> .
> .
> .
>
> stop_and_output_stopwatch(&execute_time_us);
>
> Is there a standard way to do this in Wireshark?  How can I output the
> accumulated time on, say, the Status Line?
>
>
> Not sure about the Status line question, but you can measure elapsed
> microseconds with something like:
>
>      guint64 start_time, end_time;
>
>      start_time = g_get_monotonic_time();
>      // ...
>      end_time = g_get_monotonic_time();
>      // ...
>      g_print("elapsed us: %" G_GUINT64_FORMAT, end_time - start_time);
>
> https://developer.gnome.org/glib/stable/glib-Date-and-
> Time-Functions.html#g-get-monotonic-time
>
>
> I think console output doesn't work on Windows for graphical applications,
> or something like that. There isn't a better standard mechanism for debug
> output in Wireshark, that I know of.
>
>
>
> You can make it appear with Edit -> Preferences -> Advanced -> change
> gui.console_open option to ALWAYS.
>
>
>
> Pascal.
>
>
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