Is this related: #7711 ?

Maybe, we'd need to profile again after #7711 is merged to see how it performs and whether still something makes it "slower".

In the profiling you linked to 63% of the time is spent in Profiler::setProfilingRunIds(), it would be great to profile without any different code being executed in Piwik.

FYI I made some changes in profiler setup in #7711 so that wouldn't happen, you can look through the branch to apply the changes locally for profiling.

EDITED

By the way did you profile with composer dump-autoload -o? It seems Composer is doing some file_exists where it shouldn't when using the classmap (though I'm not 100% certain)

The profile is not really relevant in this case. The profile shows it took 50ms or more but the 20-40ms I mentioned is with no profiling enabled etc. This used to be 4ms.

Right, but w/o an accurate profile, how will we diagnose + test the issue? Can you tell us what Piwik version was used when the tracker was fast?

I'm just saying there seems to be a regression that's all. One can at least see where some time is spent and everything else has to be looked into when actually working on this issue anyway.

I reckon this was around December 2014 when the QueuedTracking plugin was built so probably 2.9.0 or 2.10.0.

Let's take a look at Tracker API performance and profile it for 2.15.0. it shouldn't take long (ie. couple hours?) to figure out if something is slow or not, and if we really regressed performance, it would be high value to make tracker faster again.

I uploaded an xhprof profile for a single pageview here: https://blackfire.io/profiles/4396e3dd-d9cf-4c48-a337-b5e4737057af/graph It looks good and seems like nothing regressed extremely.

Here is a profile taken with xhprof of a bulk request (with 133 requests): https://blackfire.io/profiles/1849a1c0-6483-4b4c-84eb-9f2d3896951c/graph. I can't tell if anything regressed but didn't find anything that worried me. A lot of time was spend in $visit->isExcluded() (27.5%) but we can probably not do much here

Time spent in Composer and loading files seems very high in your first profile, I already asked this but did you optimize the autoloader? And did you remove dev dependencies (as they can overload the classmap and make a difference in short lived processes)? Also I don't know if you still use PHP 5.4 but did you use an opcache (and warm it up)? (especially since Vagrant's vboxfs, or even nfs, are much slower than native FS)

Anyway good to know there is no regression.

yes autoloader optimized, I didn't remove dev dependencies but that's not really important in this case. It's PHP 5.5 with opcache and warmed up of course