Reflection and performance in web

Question

We know Reflection is a quite expensive engine. But nevertheless ASP.NET MVC is full of it. And there is so much ways to use and implement additional reflection-based practices like ORM, different mappings between DTO-entities-view models, DI frameworks, JSON-parsing and many many others.
So I wonder do they all affect performance so much that it is strongly recommended to avoid using reflection as much as possible and find any another solutions like scaffolding etc? And what is the tool to perform server's load testing?

Answer 1

There's nothing wrong with Reflection. Just use it wisely, a.k.a cache the results so that you don't have to perform those expensive calls over and over again. Reflection is used extensively in ASP.NET MVC. For example when the controller and action names are parsed from the route, Reflection is used to find the corresponding method to invoke. Except that once found, the result is cached so that the next time someone requests same controller and action name, the method to be invoked is fetched from the cache.

So if you are using a third party framework check the documentation/source code whether it uses reflection and whether it caches the results of those calls.

And if you have to use it in your code, same rule applies => cache it.

Answer 2

For stress testing, this SO post gives quite a few possibilities: Stress Testing ASP.Net application.

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I have thought about this question myself, and come to the following conclusions:

• Most people don't spend their days resubmitting pages over and over again. The time the user spends reading and consuming pages which at worst contain a few Ajax calls is minimal when taken into context with the time spent visiting an actual website. Even if you have a million concurrant users of your application, you will generally not have to deal with a million requests at any given time.

• The web is naturally based on string comparisons... there are no types in an HTTP response, so any web application is forced to deal with these kinds of tasks as a fact of everyday life. The fewer string comparisons and dynamic objects the better, but they are at their core, unavoidable.

• Although things like mapping by string comparison or dynamic type checking are slow, a site built with a non-compiled, weakly-typed language like PHP will contain far more of these actions. Despite the number of possible performance hits in MVC compared to a C# console application, it is still a superior solution to many others in the web domain.

• The use of any framework will have a performance cost associated with it. An application built in C# with the .NET framework will for all intents and purposes not perform as well as an application written in C++. However, the benefits are better reliability, faster coding time and easier testing among others. Given how the speed of computers has exploded over the past decade or two, we have come to accept a few extra milliseconds here and there in exchange for these benefits (which are huge).

Given these points, in developing ASP.NET MVC applications I don't avoid things such as reflection like the plague, because it is clear that they can have quite a positive impact on how your application functions. They are tools, and when properly employed have great benefits for many applications.

As for performance, I like to build the best solution I can and then go back and run stress tests on it. Maybe the reflection I implemented in class X isn't a performance problem after all? In short, my first task is to build a great architecture, and my second is to optimise it to squeeze every last drop of performance from it.