Recently we got a bug report about the performance of Windsor when registering large number of components (thousands). I decided to sit down and investigate this, and found out something that was troublesome.
Internally, registering a component would trigger a check for all registered components that are waiting for a dependency. If you had a lot of components that were waiting for dependency, registering a new component degenerated to an O(N^2) operation, where N was the number of components with waiting dependencies.
Luckily, there was no real requirement for an O(N^2) operation, and I was able to change that to an O(N) operation.
Huge optimization win, right?
In numbers, we are talking about 9.2 seconds to register 500 components with no matching dependencies. After the optimization, we dropped that to 500 milliseconds. And when we are talking about larger number of components, this is still a problem.
After optimization, registering 5,000 components with no matching dependencies took 44.5 seconds. That is better than before (where no one has the patience to try and figure out the number), but I think we can improve up it.
The problem is that we are still paying that O(N) cost for each registration. Now, to suppose systems that already uses Windsor, we can’t really change the way Windsor handle registrations by default, so I came up with the following syntax, that safely change the way Windsor handles registration:
var kernel = new DefaultKernel();
for (int i = 0; i < 500; i++)
kernel.AddComponent("key" + i, typeof(string), typeof(string));
Using this method, registering 5,000 components drops down to 2.5 seconds.
I then spent additional time finding all the other nooks and crannies where optimizations hid, dropping the performance down to 1.4 seconds.
Now, I have to say that this is not linear performance improvement. Registering 20,000 components will take about 25 seconds. This is not a scenario that we worry over much about.
The best thing about the non linear curve is that for a 1,000 components, which is what we do care about, registration takes 240 milliseconds. Most applications don’t get to have a thousand components, anyway.
There are also other improvements made in the overall runtime performance of Windsor, but those would be very hard to notice outside of a tight loop.