[ltt-dev] UST Test

[Pierre-Marc Fournier]

On 09/03/2010 01:37 PM, David Goulet wrote:
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> Hi everyone,
>
> I think we had some time ago a discussion about that but now I want to fix this
> properly and for good. The current benchmark test in the UST git is :
> 1) Only testing trace_mark
> 2) Using syscalls
>
> This makes the per event time goes ~1.1ms for 1 millions events. I did some time

Are you sure about this? I get around 1 us/event.

> ago another benchmark test that tested trace_mark, tracepoint with trace_mark
> and custom probe but _without_ syscalls (only math calculation) and the time
> dropped to ~200ns per event.

Can you explain why system calls make such a big difference in per-event 
times? I find it disturbing and I am reluctant to remove them from the 
benchmark just because this results in better figures without knowing 
what is happening.

>
> So, I don't question the current benchmark test but perhaps it should be good to
> design a test that first will test all "marking" technology (including soon to
> come trace_event), second that will use multiple use case scenario (like
> syscalls, regular calculation, string manipulation, I/O, ...) because each of
> these test gives different results.
>
> We have NO test case that test all four (marker, TP, custom, TE) and I think
> this should be VERY important because I just found out that the the
> trace_mark_tp was not working since the changes made by Nils with the data
> pointer by using some old test I had. This should be detected with the
> tests/runtests script at each new release or/and pull commit.

Good ideas, but I think tests and benchmarks should be separate 
programs. Probably there should be one test per instrumentation type and 
one benchmark per instrumentation type.

pmf

>
> Cheers
> David
> - --
> David Goulet
> LTTng project, DORSAL Lab.
>
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