Hi Jérémie, thanks for your feedback.
I've added only a loop to the end of the demo programm. Frequence scaling I can't imagine on my dektop machine. It is a jump between 350ns and 800ns. In the loop below all the events of one test run are of equal time distance, either slow or fast. Wolfgang R. https://github.com/lttng/lttng-ust/blob/master/doc/examples/demo/demo.c ... tracepoint(ust_tests_demo, starting, 123); for (i = 0; i < 5; i++) { netint = htonl(i); tracepoint(ust_tests_demo2, loop, i, netint, values, text, strlen(text), dbl, flt); } tracepoint(ust_tests_demo, done, 456); tracepoint(ust_tests_demo3, done, 42); for (i = 0; i < 300; i++) { if(i % 10 == 0) { tracepoint(ust_tests_demo, done, i); <========= } } fprintf(stderr, " done.\n"); return 0; } > Gesendet: Freitag, 03. April 2015 um 16:22 Uhr > Von: "Jérémie Galarneau" <[email protected]> > An: "Wolfgang Rostek" <[email protected]> > Cc: "[email protected]" <[email protected]> > Betreff: Re: [lttng-dev] major variations in perfomance figures > > On Tue, Mar 31, 2015 at 3:46 PM, Wolfgang Rostek <[email protected]> > wrote: > > Hi all, > > > > I did a first perfomance test extending the demo example > > by tracing 30 simple integers in a loop. > > > > For a similar CPU (i5 quad core 2.8GHz) I saw values > > mentioned around 250ns in the forum. > > > > I've tried the test several time and could come down > > to about 350ns. The machine was almost idle for all > > tests. > > > > What makes me wonder is a large variation with frequent > > runs giving me 750-800ns. > > > > Not the absolute time but the variations isn't clear > > to me. From my understanding the caller path is more > > or less straight to shared memory. Why do different > > runs show more than double the time for the traces? > > Good question. Can you share the benchmark's code? > Also, make sure frequency scaling is disabled on your system; it could > explain these kinds of variations. > > Jérémie > > > > > Wolfgang R. > > > > > > > > _______________________________________________ > > lttng-dev mailing list > > [email protected] > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > -- > Jérémie Galarneau > EfficiOS Inc. > http://www.efficios.com > _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
