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5. Performance
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Important note
THE DATA PROVIDED BELOW IS OBSOLETE AS OF V 3.0.0.
Since it was computed, a lot has changed: PHP 7, change of structure in the profiler, changes in PHP and the operating systems. We will probably not get around to making a comprehensive performance test too soon, so YMMV.
Important note
Upon recent tests, running on Oracle VirtualBox yields overheads as much as 20X greater than in the statistics shown below. For this reason, we recommend against running profilers on this virtualization platform, as the results will likely be distorted.
The main goals of the PHP profiler are to provide light-weight PHP profiling, while at the same time providing full call-trace logs and cycle detection. In the following table you can see how it does against the other PHP profilers. It lists the execution time of a trivial typical getter:
class a{ var $x=5; function getX(){ return $x; } } $a=new a; for($i=0;$i<$COUNT;$i++){ $x=$a->getX(); }
over 40,000 iterations; the absolute times expressed are measured on a php 5.3 running on a Centos 6 x86 virtualized over an Intel i5 processor. They should serve as a raw appreciation of how much overhead each function call will carry.
| Profiler: | none | web3tracer 2.2.0 | xhprof | xdebug 2.2.1 |
| Call time: | 779 ns | 1026 ns | 1407 ms | 27,710 ns |
| Call time overhead: | - | 247 ns | 628 ns | 26,965 ns |
| % overhead: | - | + 32 % | + 81 % | + 3519 % |
Please note, if the above data is relevant to you, it might also be relevant that in web3tracer the function call overhead is distributed about 50-50 between the calling function and the called function internal times, in the resulting profile.
We can see a great improvement in the PHP Profiler's overhead, which should lead to less measuring errors. You will not be tempted to optimize things that don't need it, justbecause they are used a lot. Using a lightweight PHP prfiler will save you the headaches.