Understanding CPU Utilization vs. CPU Load and Troubleshooting High Load Scenarios

Difference Between CPU Utilization and CPU Load

CPU utilization measures the percentage of CPU time slices actually used by processes, while CPU load represents the average number of tasks either running or waiting for CPU over a period.

Utilization reflects real‑time usage; load reflects current and near‑future demand, so a program can drive utilization to 100% but keep load near 1 if it is the only active task.

On a single‑core system a load of 1 means full capacity; values above 1 indicate queuing. On multi‑core systems the threshold scales with core count (e.g., 4 cores can handle load up to 4 comfortably).

Typical commands to view these metrics are uptime , w , and top .

How to Check Physical CPU and Core Counts

Physical CPU count:

cat /proc/cpuinfo| grep "physical id"| sort | uniq| wc -l

Core count per physical CPU:

cat /proc/cpuinfo| grep "cpu cores" | uniq

Logical CPU count:

cat /proc/cpuinfo| grep "processor"| wc -l

When Load Is High but Utilization Is Low

This usually indicates many tasks are blocked, often due to I/O bottlenecks or unindexed MySQL queries causing extensive disk waits.

Scenario 1: Excessive Disk I/O

Heavy read/write requests push many processes into uninterruptible sleep (state D), raising load while CPU stays idle.

Scenario 2: MySQL Without Indexes or Deadlocks

Large table scans or deadlocks generate I/O wait, increasing load without raising CPU usage.

Use top to confirm high load with low utilization, then ps -aux to look for processes in state D.

When Load Is Low but Utilization Is High

This suggests a few CPU‑bound tasks are running for long periods, often due to inefficient, compute‑intensive code.

Identify the culprit with top , locate the high‑usage process, and inspect its code.

Diagnosing 100% CPU Utilization

1. Find the high‑usage process

top

2. List threads of that process

top -Hp pid

3. Convert thread ID to hexadecimal

printf "0x%x\n" 74317

results in 0x1224d

4. Locate the offending code

jstack 72700 | grep '0x1224d' -C5 --color

Note: jstack works on Java process PIDs, not thread IDs.

Common Linux Commands

File and Directory Operations

ls , ls -a , ls -l

touch

cat

more , less

tail -fn 100 xx.log

Permission Management

chmod +x filename (symbolic) or chmod 777 filename (numeric).

chown user:group filename

Compression and Archiving

zip test.zip file (use -r for directories)

unzip file.zip

gzip file (or gzip -c file > file.gz )

tar -cvf archive.tar files , tar -xvf archive.tar , or combined tar -zcvf archive.tar.gz files and tar -zxvf archive.tar.gz

Understanding the distinction between packing (tar) and compression (gzip) helps manage large collections of files efficiently.

For more detailed examples and screenshots, refer to the original article.