FAQ

Why this website?

There a lot of materials online on performance optimization. However, knowing where to start could be still quite troublesome, and as a lot of details are involved, the presentation could be a bit boring. This website hopefully provides a good and fun starting points for beginner.

The website serves as an introduction to certain topic regarding performance optimization. It is NOT supposed to be used as a reference on how code should be written.

How accurate is microbenchmark?

There might be a few reasons that you don't want to trust the benchmark result at face value, even if the code is "correct" (if you find any mistake, feel free to send a MR).

One reason is the benchmark result varies a lot on the compiler/hardware/existing software. You always want to run them yourself at the target setup of your application.

Interpreting the result is another headche:

• It usually does not take into account the performace when it is mixed up with other code, where resources are shared for the whole app. For example, memory alignment could look good at microbenchmark, but too many aligned memory could lead to increase in cache miss due to cache assosication.
• At smaller scale, some effect might be magnified compared to in normal situation. For example, instruction address could cause a large gain/loss in performance at microbenchmark. As such, you always want to look at the generated asm, CPU perf counter, etc to understanding the root cause of speed differences.

Should I change my code like the faster example?

No. You should benchmark the whole codebase in a realistic workloads. Microbenchmark is not always a reliable shortcut.