Prerequisites

• SSH access to the ESXi host
• Administrative privileges
• Basic familiarity with ESXi CLI tools

1. Monitor CPU Usage with esxtop

The esxtop utility provides real-time performance monitoring.

Launch esxtop

esxtop

Switch to CPU View

Press:

p

Add Advanced CPU Metrics (%A/MPERF)

1. Press f to open field selection
2. Press f again
3. Press Enter to confirm

This enables additional CPU performance counters for deeper analysis.

2. View CPU Hardware Information

Use esxcli to display detailed CPU hardware information:

esxcli hardware cpu list

This command provides details such as:

• CPU model
• Core count
• Thread count
• Frequency

3. Retrieve Per-CPU Performance Data Using vsish

Check a Single CPU Core

vsish -e get /power/pcpu/0/perf

This displays performance metrics for CPU core 0.

Check All CPU Cores

vsish -e get $(printf 'power/pcpu/%sperf ' $(vsish -e ls power/pcpu))

This command retrieves performance data for all physical CPU cores.

4. Calculate Average CPU Performance

Use the following command to calculate the average CPU performance percentage across all cores:

vsish -e get $(printf 'power/pcpu/%sperf ' $(vsish -e ls power/pcpu)) | awk '/current/ {cpus+=1; total+=$6} END {print total/cpus "%"}'

This processes the vsish output and calculates the average "current" CPU performance.

5. Identify Maximum CPU Performance

To find the highest CPU performance value across all cores:

vsish -e get $(printf 'power/pcpu/%sperf ' $(vsish -e ls power/pcpu)) | awk '/current/ {if($6 > max) max=$6} END {print max}'

This identifies the peak CPU utilization value among all cores.

Best Practices

• Use esxtop for real-time monitoring during performance issues
• Use vsish for detailed low-level metrics
• Correlate CPU metrics with workload activity
• Monitor both average and peak CPU usage

Summary

By combining esxtop, esxcli, and vsish, administrators can gain both high-level and low-level visibility into CPU performance on ESXi hosts.