optimisations are frequently added to ikiwiki, some of them yielding
*enormous* speed increases.
+## run ikiwiki in verbose mode
+
+Try changing a page, and run ikiwiki with `-v` so it will tell you
+everything it does to deal with that changed page. Take note of
+which other pages are rebuilt, and which parts of the build take a long
+time. This can help you zero in on individual pages that contain some of
+the expensive things listed below.
+
## expensive inlines
Do you have an archive page for your blog that shows all posts,
\[[!inline pages="blog/* and link(tag)" show=0 archive=yes quick=yes]]
-Only downsides: This won't show titles set by the [[!ikiwiki/directive/meta]]
+Only downsides: This won't show titles set by the [[ikiwiki/directive/meta]]
directive. And there's no RSS feed for users to use -- but if this page
is only for the archives or tag for your blog, users should be subscribing
to the blog's main page's RSS feed instead.
keep adding pages.
First, consider removing the "show=title". Then the map will not show page
-titles set by the [[!ikiwiki/directive/meta]] directive -- but will also
+titles set by the [[ikiwiki/directive/meta]] directive -- but will also
only need to be generated when pages are added or removed, not for every
page change.
to be slow. But using it to map a few related pages is probably fine.
This site's own [[plugins/linkmap]] rarely slows it down, because it
-only shows the [[index]] page, and the small set of pages that link to it.
+only shows the index page, and the small set of pages that link to it.
That is accomplished as follows:
\[[!linkmap pages="index or (backlink(index)"]]
Be aware that the [[plugins/search]] plugin has to update the search index
whenever any page is changed. This can slow things down somewhat.
+## cgi overload workaround
+
+If the ikiwiki.cgi takes a long time to run, it's possible
+that under load, your site will end up with many
+of them running, all waiting on some long-running thing,
+like a site rebuild. This can prevent the web server from doing anything
+else.
+
+A workaround for this problem is to set `cgi_overload_delay` to
+a number of seconds. Now if ikiwiki.cgi would block waiting
+for something, it will instead display a Please wait message (configurable
+via `cgi_overload_message`, which can contain arbitrary html),
+and set the page to reload it after the configured number of seconds.
+
+This takes very little load, as it all happens within compiled C code.
+Note that it is currently limited to GET requests, not POST requests.
+
## scaling to large numbers of pages
Finally, let's think about how huge number of pages can affect ikiwiki.
new and changed pages. This is similar in speed to running the `find`
command. Obviously, more files will make it take longer.
+ You can avoid this scanning overhead, if you're using git, by setting
+ `only_committed_changes`. This makes ikiwiki -refresh query git for
+ changed files since the last time, which tends to be a lot faster.
+ However, it only works if all files in your wiki are committed to git
+ (or stored in the [[/plugins/transient]] underlay).
+
* Also, to see what pages match a [[ikiwiki/PageSpec]] like "blog/*", it has
to check if every page in the wiki matches. These checks are done quite
quickly, but still, lots more pages will make PageSpecs more expensive.
* The backlinks calculation has to consider every link on every page
- in the wiki. (In practice, most pages only like to at most a few dozen
+ in the wiki. (In practice, most pages only link to at most a few dozen
other pages, so this is not a `O(N^2)`, but closer to `O(N)`.)
* Ikiwiki also reads and writes an `index` file, which contains information
If your wiki will have 100 thousand files in it, you might start seeing
the above contribute to ikiwiki running slowly.
+
+## profiling
+
+If you have a repeatable change that ikiwiki takes a long time to build,
+and none of the above help, the next thing to consider is profiling
+ikiwiki.
+
+The best way to do it is:
+
+* Install [[!cpan Devel::NYTProf]]
+* `PERL5OPT=-d:NYTProf`
+* `export PER5OPT`
+* Now run ikiwiki as usual, and it will generate a `nytprof.out` file.
+* Run `nytprofhtml` to generate html files.
+* Those can be examined to see what parts of ikiwiki are being slow.