Hugo is fast, but ineffecinet templates can make it slower. For checking the performance you can use the below commands.

• Use hugo --logLevel debug to display debug information, warning, and error message.

• Use hugo --templateMetrics to check for slow templates. This will show the time it takes to render each template.

• Use hugo --gc (garbage collection) to clean up unused files, which might help reduce build time.

• Use debug.Timer to determine the execution time of a block of code. And use the hugo --logLevel info info command line flag when you build the site.

{{ $t := debug.Timer "TestSqrt" }}
{{ range seq 2000 }}
  {{ $f := math.Sqrt . }}
{{ end }}
{{ $t.Stop }}

References

Hugo Docs