ref: 794e1f9e728ca49a604997294b476547c2b31898
dir: /docs/content/en/troubleshooting/build-performance.md/
---
title: Build Performance
linktitle: Build Performance
description: An overview of features used for diagnosing and improving performance issues in site builds.
date: 2017-03-12
publishdate: 2017-03-12
lastmod: 2017-03-12
keywords: [performance, build]
categories: [troubleshooting]
menu:
docs:
parent: "troubleshooting"
weight: 3
slug:
aliases: []
toc: true
---
{{% note %}}
The example site used below is from https://github.com/gohugoio/hugo/tree/master/examples/blog
{{% /note %}}
## Template Metrics
Hugo is a very fast static site generator, but it is possible to write
inefficient templates. Hugo's *template metrics* feature is extremely helpful
in pinpointing which templates are executed most often and how long those
executions take **in terms of CPU time**.
| Metric Name | Description |
|---------------------|-------------|
| cumulative duration | The cumulative time spent executing a given template. |
| average duration | The average time spent executing a given template. |
| maximum duration | The maximum time a single execution took for a given template. |
| count | The number of times a template was executed. |
| template | The template name. |
```
▶ hugo --templateMetrics
Started building sites ...
Built site for language en:
0 draft content
0 future content
0 expired content
2 regular pages created
22 other pages created
0 non-page files copied
0 paginator pages created
4 tags created
3 categories created
total in 18 ms
Template Metrics:
cumulative average maximum
duration duration duration count template
---------- -------- -------- ----- --------
6.419663ms 583.605µs 994.374µs 11 _internal/_default/rss.xml
4.718511ms 1.572837ms 3.880742ms 3 indexes/category.html
4.642666ms 2.321333ms 3.282842ms 2 posts/single.html
4.364445ms 396.767µs 2.451372ms 11 partials/header.html
2.346069ms 586.517µs 903.343µs 4 indexes/tag.html
2.330919ms 211.901µs 2.281342ms 11 partials/header.includes.html
1.238976ms 103.248µs 446.084µs 12 posts/li.html
972.16µs 972.16µs 972.16µs 1 _internal/_default/sitemap.xml
953.597µs 953.597µs 953.597µs 1 index.html
822.263µs 822.263µs 822.263µs 1 indexes/post.html
567.498µs 51.59µs 112.205µs 11 partials/navbar.html
348.22µs 31.656µs 88.249µs 11 partials/meta.html
346.782µs 173.391µs 276.176µs 2 posts/summary.html
235.184µs 21.38µs 124.383µs 11 partials/footer.copyright.html
132.003µs 12µs 117.999µs 11 partials/menu.html
72.547µs 6.595µs 63.764µs 11 partials/footer.html
```
{{% note %}}
**A Note About Parallelism**
Hugo builds pages in parallel where multiple pages are generated
simultaneously. Because of this parallelism, the sum of "cumulative duration"
values is usually greater than the actual time it takes to build a site.
{{% /note %}}
## Cached Partials
Some `partial` templates such as sidebars or menus are executed many times
during a site build. Depending on the content within the `partial` template and
the desired output, the template may benefit from caching to reduce the number
of executions. The [`partialCached`][partialCached] template function provides
caching capabilities for `partial` templates.
{{% tip %}}
Note that you can create cached variants of each `partial` by passing additional
parameters to `partialCached` beyond the initial context. See the
`partialCached` documentation for more details.
{{% /tip %}}
[partialCached]:{{< ref "/functions/partialCached.md" >}}