At a high level, CPU load is a measure of the amount of processing power that is being used by the system. More specifically, it is a measure of the amount of work that the system is doing. The higher the CPU load, the more work the system is doing.
There are a few different ways to measure CPU load. One common way is to track the number of processes that are running on the system. This can be done by looking at the output of the ps command. Another way to measure CPU load is to track the amount of time that the CPU spends in different states. This can be done by looking at the output of the top command.
CPU load can be measured using a variety of tools, but one of the most common tools is sar. Sar stands for System Activity Reporter and it can be used to generate reports on a variety of system activity metrics, including CPU load.
To use sar, you need to have root access to the server. Once you have root access, you can use sar to generate reports on demand or you can use it to generate periodic reports that are logged to disk.
What is CPU Load?
CPU load is a measure of how much processing power a computer is using. A high CPU load is an indication that there are a lot of processes running on the computer. Linux is a multitasking operating system, which means that multiple processes can be running at the same time. When there are a lot of processes running, the CPU can get overwhelmed and start to slow down.
User vs System vs I/O vs Idle CPU time
User time is the amount of time that the CPU spends running code in user-space programs. User-space programs are pretty much everything that isn’t part of the operating system kernel. System time is the amount of time that the CPU spends running code in the operating system kernel. This code includes things like device drivers, interrupt handlers, and system calls. I/O time is the amount of time that the CPU spends waiting for I/O operations to complete. This could include things like disk or network activity. Idle time is the amount of time that the CPU is not doing anything at all.
The first thing to do when trying to understand CPU load is to look at all four of these metrics together. To get an idea of what normal looks like for your system, run sar -u -r -d -n ALL 5 3 as root and look at the averages for all four metrics:
Average: all 1.60 0.13 0.06 0.21
Average: all 1.54 0.14 0.05 0.21
Average: all 1.51 0.15 0.06 0
How to Monitor CPU Load?
If you are running a Linux based server, it’s important to understand what CPU load is and how to monitor it. CPU load is the amount of processing power that is being used by the system. A high CPU load can slow down your server and cause it to become unresponsive.
Using the top command
The top command provides a dynamic real-time view of a running system. It can display system summary information as well as a list of processes or threads currently being managed by the Linux kernel. The types of system information displayed by top include the total number of processes, the number of sleeping processes, the number of running processes, the number of active CPU cores, the overall CPU usage, user-based CPU usage, and system-based CPU usage.
Top also provides a limited interactive interface for process management, allowing users to renice or kill specific processes. By default, top sorts processes by theircurrent CPU usage.
Using the sar command
Load is the average number of processes that are either in a runnable or uninterruptible state. A process in a runnable state is either using the CPU or waiting to use the CPU. A process in an uninterruptible state is waiting for some I/O access, usually involving hardware devices. The output from the uptime command includes load averages for the past 1, 5, and 15 minutes.
To see more detailed statistics, you can use the sar command with different options. As an example, to see real-time data every 30 seconds for 3 minutes, you can use the following command:
“`
sar -u 30 3
“`
The above command gives you an overview of your CPU utilization during that time period. The total number of CPUs is 4 on this server (note the column labelled all), and we can see that on average around 70% of CPUs were idle during that time period.
Now suppose you want to see all available statistics about your server’s load for today:
“`
sar -A
“`
Using the htop command
htop is an interactive process viewer for Linux. It allows users to view and monitor all processes running on the system, as well as kill, send signals, and change process priorities. In this article, we will show you how to use htop to monitor CPU load on your Linux server.
To install htop on Ubuntu, run the following command:
sudo apt-get install htop
To install htop on CentOS, run the following command:
sudo yum install htop
Once htop is installed, you can launch it by running the “htop” command. By default, htop displays processes in a user-friendly view, sorted by CPU usage.
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 36 root 20 0 9244 4096 1000 S 0 0.1 0:00.03 bash 277 root 20 0 96728 12272 7536 S 0 1.2 0:03.19 sshd
Conclusion
In conclusion, it is important to understand what Linux CPU load is and how it can be monitored in order to ensure your server is running smoothly. Load averages can be monitored using the top command or by looking at the /proc/loadavg file. If you see a high load average, it is important to investigate the cause so that you can take steps to fix the problem.
