[lttng-dev] Cost of user space tracepoint()

[ChitlurSrinivasa, Venkatesh]

I am sure you guys will do regular performance runs on different versions of LTTng, but I couldn't find any links to the latest results. I was trying to find the cost of a tracepoint() recording one integer. On CPU Intel Xeon E5-2680 v2 @ 2.80GHz?, running Linux 3.6.11? and lttng 2.4.1,  I am getting about 927 cycles (9270692144 cycles for 10000000? iterations). This seems to be lot higher than the documented results . In the paper https://lttng.org/files/papers/desnoyers.pdf  the average cost of tracepoint() with older ltt-usertrace-fast tracepoint is 297 cycles. Another link <http://lttng.org/files/thesis/desnoyers-thesis-defense-2009-12-e1.pdf> http://lttng.org/files/thesis/desnoyers-thesis-defense-2009-12-e1.pdf says cache hot tracepoint() cost is 238 cycles.


It appears that in spite of better cpu, and newer version of lttng and kernel I am seeing higher cost. Am I missing something here? Do I need to enable certain features of kernel/cpu ?


VBabu
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