Bottlenecking is a performance problem that is caused by one or more components limiting the performance of an entire computer system. The term was named after the flow of liquid out of a bottle, where the narrow width of the neck of the bottle compared to the rest of the body limits the flow of liquid – a similar thing can happen in a computer when it comes to performance.
The concept of bottlenecking applies to all systems where a task doesn’t complete instantly, as at least one factor will always be limited performance. To achieve the best possible performance, the bottlenecks in a system need to be minimized as much as possible.
For example, when building a gaming computer, the graphics card is one of the most important parts of the build. However, if you spend too much money on the graphics card and use budget-tier components for the rest of the computer, you may not be able to get the best performance out of your GPU. This is because the GPU relies on resources being provided to it. If other system components such as the RAM or CPU can’t provide it data fast enough, it will have to spend time idling, waiting to receive that data, which for the user means low performance.
In this case, the poor performance of the CPU or RAM would be the bottleneck. To prevent this bottleneck, you should balance the budget of your PC so that you purchase parts that can provide data fast enough for your GPU to run at full speed. Once this is the case, and your GPU can run at full speed consistently, it is technically the bottleneck, limiting your performance. Just remember that there will always be at least one factor limiting the performance of any system, so your goal is to balance that, so that not too much possible performance is wasted.
In another example, racing cars want to take corners as fast as possible, they are, however, limited by the grip provided by their tires. To reduce the overall lap time bottleneck that is their lack of grip, racing cars often use wings to provide downforce, increasing the grip. With bigger wings, you get more grip, allowing you to take corners faster. On high-speed straights, however, the wing also applies drag, reducing the overall top speed of the car.
To minimize the lap time bottlenecks, that are lack of grip in corners and too much drag at high-speed, teams must optimize the wing or wings on the car to provide the best possible combination of straight line and cornering speed to get the fastest lap times.