How to Calculate Linux System Load Average in percentage

• In the world of Linux system administration, monitoring system load is a fundamental task. It helps in understanding how well the system is performing and whether it is under any strain. 

• Today, we're going to explore a simple Bash script that can provide a clear snapshot of the system's load average and how this translates to CPU usage. 

• We will also learn how to figure out this CPU use in percentage. This script is a powerful tool for Linux system administrators.

Understanding Key CPU Metrics:

1. CPU Usage Percentage

• This metric indicates the percentage of the CPU's capacity currently in use.

2. Load Average

• Load average represents the average system load over a specified period (1, 5, and 15 minutes).

• For a system with a single CPU, a load average of 1.0 signifies full utilization.

• On a multi-core system, a load average equal to the number of cores means full utilization.

• Values exceeding the number of cores indicate queued processes waiting for CPU time, potentially leading to slower performance.

3. Context Switches

• This metric counts the number of times the CPU switches from processing one thread or process to another.

• High numbers of context switches may indicate that the CPU is spending a lot of time switching between tasks, which can reduce efficiency.

4. CPU Time Breakdown

• User Time: Time spent on user-mode operations (non-kernel code).

• System Time: Time spent on kernel-mode operations.

• Idle Time: Time when the CPU is not being used.

• I/O Wait Time: Time waiting for I/O operations to complete.

5. Interrupts Per Second

• This measures the number of hardware interrupts that the CPU receives per second.

• A high number of interrupts could indicate busy or malfunctioning hardware

Important key Metrics of the script:

Fetching Load Averages: 

• The script uses the uptime command to fetch load averages for 1, 5, and 15 minutes.

Determining CPU Cores:

• The number of CPU cores is fetched using the nproc command.

• The load average needs to be evaluated in the context of the available cores.

Calculating Percentages:

• The script then calculates the load percentage for each interval. 

• This is done by dividing the load average by the number of CPU cores and multiplying by 100.

• Formula: It uses the formula (load average / number of CPU cores) * 100 to calculate this percentage.

Important Note:

• Based on the script output, if the system load exceeds 100%, it indicates an abnormal state where multiple processes are in the run queue, waiting for CPU resources. This suggests that the system is overloaded. 

• Conversely, if the system load is less than 100%, it can be considered normal, indicating that the system is operating within its CPU usage threshold and is not overloaded.

Linux System Load Average bash script:

#!/bin/bash

#Author: virtualnetworkingconcept.com

# Get the CPU load averages

load_avg_1min=$(uptime | awk -F'load average: ' '{print $2}' | cut -d ',' -f1 | tr -d ' ')

load_avg_5min=$(uptime | awk -F'load average: ' '{print $2}' | cut -d ',' -f2 | tr -d ' ')

load_avg_15min=$(uptime | awk -F'load average: ' '{print $2}' | cut -d ',' -f3 | tr -d ' ')

# Get the number of CPU cores

cpu_core=$(nproc)

# Calculate percentages

percentage_1min=$(echo "scale=2; ($load_avg_1min / $cpu_core) * 100" | bc)

percentage_5min=$(echo "scale=2; ($load_avg_5min / $cpu_core) * 100" | bc)

percentage_15min=$(echo "scale=2; ($load_avg_15min / $cpu_core) * 100" | bc)

# Print output in table format

echo "+----------------+--------------+-----------------+"

echo "| Time Intervals | Load Average | System Load (%) |"

echo "+----------------+--------------+-----------------+"

printf "| %-14s | %-12s | %-15s |\n" "1 minute" "$load_avg_1min" "$percentage_1min%"

printf "| %-14s | %-12s | %-15s |\n" "5 minutes" "$load_avg_5min" "$percentage_5min%"

printf "| %-14s | %-12s | %-15s |\n" "15 minutes" "$load_avg_15min" "$percentage_15min%"

echo "+----------------+--------------+-----------------+"

Script Output:

centos# sh linux_load_avg.sh

+----------------+--------------+-----------------+

| Time Intervals | Load Average | System Load (%) |

+----------------+--------------+-----------------+

| 1 minute       | 2.60         | 130.00%         |

| 5 minutes      | 2.56         | 128.00%         |

| 15 minutes     | 1.43         | 71.00%          |

+----------------+--------------+-----------------+

Conclusion:

• If you are taking care of Linux servers, it's very important to know about CPU usage. 

• Good CPU usage means your servers will work better and more reliably.

• This simple yet effective Bash script provides a snapshot of the system's load average and its impact in terms of CPU usage. 

• By regularly running this script, system administrators can stay ahead in managing system resources efficiently, ensuring that the Linux servers remain healthy and perform optimally.