Andrew Schweitzer <a.schweitzer.grps <at> gmail.com> writes:
Using GetTickCount and GetThreadTimes on Windows XP Pro, recorded time to execute some simple pieces of logging code in a loop. Divided by loop iterations to get time per iteration. This is a 3Ghz Pentium. Not sure how good these tests are, but here's the results:
results: elapsed ms thread time ms ns / call
(GetTickCount)
(GetThreadTimes) (in thread) cout 1329 421 42100 enabled log 1469 453 45300 cout "disabled" 15 15 15 disabled log 531 531 531
Compiler/version? Optimization settings? How long does a single or a very small number of iterations of the disabled cout and disable log take?
Here's a little detail on tests cout, 10,000 times, l_dw increments each loop: cout << l_dw << endl;
enabled log, 10,000 times: //outside loop: enable_logs("lgTest"); //in loop: BOOST_SCOPEDLOG(l_lgTest) << l_dw << endl;
cout "disabled", 1,000,000 times: //outside loop: bool l_bEnabled = false; //in loop: if(l_bEnabled) { cout << l_dw << endl; }
The disabled cout test, if it really is as simple a bit of code as that should take something close to 0 time to execute - which it does. If you put the if (l_bEnabled) test in a separate compilation unit to the loop body is performance the same?
disabled log, 1,000,000 times: //outside loop: disable_logs("lgTest"); //this not in loop //in loop: BOOST_SCOPEDLOG(l_lgTest) << l_dw << endl;
This involves at least the creation and destruction of a small temporary object, a function call to a separate compilation unit and an inderection through a shared ptr (not expensive) 500 odd ns seems broadly ok for that I guess - so something like 2 million disabled log messages/second.... Don't accidentally enable all logs/that log.... If you have a system with 100 logs, and only 1 enabled, the other 99 logs (being called at the same rate) are using the same amount of CPU as your 1 enabled log - not too bad - not as good as it could be either I'd guess. Some performance test should be added to the code before it is released - what enabled/disabled performance ratio do you think is needed for a "pass"? What sort of "nop function" do you think the disabled log needs to be equivalent to to pass?