Practical development experience: How to reduce CPU usage

In software development and performance testing, CPU utilization is a very important indicator, in the end what factors will lead to higher CPU utilization? What other means can reduce the CPU occupancy rate? This article is "Jhuster's column" of "actual combat development experience" series of another article, a brief summary of the CPU utilization of those things.

1. How do I test CPU usage?

First of all, we have to learn how to test the CPU utilization of the program, here is simply the most basic method:

On Windows, you can bring up task Manager from the Ctrl+alt+del combination, and then view the details of the specified process.

Linux/android platform, you can enter the command line: Top command, find the specified process.

Note that when testing, there are usually several sets of conditions to test, such as: idle, medium load operation, high load operation ...

2. What are the factors that lead to higher CPU usage?

(1) Complex calculation

Run some algorithm processing, such as: Audio and video codec, image processing, scientific calculation and so on, especially some floating point number of operations.

(2) Continuous CPU consumption

Some high-priority processes/threads continue to occupy the CPU, rarely or never sleep, similar to while (1) {}

(3) Data copy

A large number of data copies are performed frequently.

(4) Frequent system calls

For example: frequently call printf print, read and write hard disk, network transceiver and so on.

3. What are the means to reduce CPU usage?

(1) Hardware acceleration

Common hardware acceleration is: Multi-core computing, GPU, DMA, audio and video hardware codec, and many hardware acceleration features require the platform to provide API or driver support, when the need to optimize the CPU occupancy rate can focus on.

(2) Learn to "give up" CPU

In the program, there are many ways to "give up" the CPU, the first is sleep, the second is the await/signal mechanism, any programming language will have a similar interface.

In addition, there is a strategy: to properly lower your process/thread priority.

(3) Avoid frequent copying of data

In multi-threaded programming, the data copy is unavoidable, but there are some techniques to reduce some unnecessary copies, the mind must have this idea, programming with more snacks.

(4) Merging some system calls

Many times, multiple prints can be merged together to print, multiple hard disk/network access requests can also be combined and sent together.

4. Summary

About the CPU occupancy of those things are introduced here, a lot of places just point to stop, and did not fully expand, we can search the relevant articles and materials to do in-depth optimization and analysis, have any questions or suggestions welcome message or letter [email protected] exchange, or follow my Sina Weibo @ Lu _ June or follow my public number (@Jhuster) to get the latest articles and information.

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Practical development experience: How to reduce CPU usage