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Linux load and load average

Most of Linux and Unix systems show system load on load average numbers. Unlike the CPU utilization it shows how many processes are waiting for resources. Where load is a real time measurement of CPU utilization load average is an average of load in a given time. Let’s understand Linux load and load average

Difference between load and load average

Each process always either executes or wait for the system resources.
Load is a numeric data represent the current computation is done by system. If your system have the load of 0 means system is idle and load 1 means fully used. Load is very frequent changes so one second you have load of 10 and other second it’s 0. That’s why we use load average means load of a given time period.

In load average every process waiting for the resources count as one means if your system has load average of 3 means one process is executing and two process are waiting for the resources.

check load average Linux

There are many utilities available on Linux for monitoring the load average and top is one of the most common command. when you tun top command at the top right corner you will see load average on 3 diff category..

load average: 3.05, 8.40, 10.00

These values represent load average of last one, five and fifteen minutes interval

Load average of last one minute: 0.30
Load average of last five minute: 8.40
Load average of last tem minute: 10.00

Let’s understand this

00.90 : form last one minute system was idle for 10% of it’s time.
08.40 : CPU was busy and 7.4 process were waiting for CPU or 740% additional load on CPU.
10.00 : CPU was busy and 9 process were waiting for CPU or 900% additional load on CPU.

All of these calculation is based on a single CPU, if you have multiple CPU calculation would be different. For example we assume we have a 2 core CPU then

00.90 : form last one minute system was idle for 45% of it’s time.
08.40 : CPU was busy and 6.4 process were waiting for CPU or 320% additional load on CPU.
10.00 : CPU was busy and 8 process were waiting for CPU or 400% additional load on CPU.

Load average is a useful measurement to identify system bottlenecks. If your system is heavily loaded it’s mean some process is wasting the resources and need to tune it or you need to upgrade the systems.

More information can be found here..

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