== *What* ==
Flamegraphs provide insight to where and how your MediaWiki component or
extension spends its time. We instrument real web requests on the MediaWiki app
servers at WMF (using php-excimer, a low-overhead sampling profiler) and
continually publish interactive SVG visuals by entrypoint (e.g. index.php,
JobQueue, ResourceLoader load.php, or rest.php API). [1] [2]
Read more about the Arc Lamp pipeline, introduced by Ori during the 2014 HHVM
migration [3], through our blog post:
https://techblog.wikimedia.org/2021/03/03/profiling-php-in-production-at-scale/
== *What's New* ==
The user interface at https://performance.wikimedia.org/php-profiling/ has
undergone major changes.
• Date: You can now choose any date in the last *2+ years*. Previously, this
was limited to 2-3 weeks. In the dropdown menu, choose "Other", and select any
date using the native datepicker. Existing URLs remain compatible.
• Source: Real-time performance data from the *MediaWiki-on-Kubernetes*
deployment is now available through here (excimer-k8s and excimer-k8s-wall).
While web traffic remains largely on bare metal (except for test2wiki),
internal MediaWiki API traffic is already partly on Kubernetes. Refer to
T333120 <https://phabricator.wikimedia.org/T333120> for work by SRE ServiceOps
(e.g. CXServer uses MediaWiki-on-Kubernetes).
• Entrypoint: *JobQueue* (RunSingleJob) is now included in the selector, plus
the new detailed breakdowns <https://phabricator.wikimedia.org/T253679> for
*EditAction*, *PreSend*, and *PostSend* are now promoted here. These were
previously available via the file browser only.
== *How* ==
The new interface is an HTML form with vanilla JavaScript to navigate you to
the right SVG.
Details at https://gerrit.wikimedia.org/r/c/performance/docroot/+/908374.
As before, we promote "good" defaults. You don't have to make any choices to
start exploring the data. Press the big blue button to instantly view the most
recent index.php flamegraph with the default settings.
--
Timo Tijhof,
Performance Team,
Wikimedia Foundation.
[1] https://wikitech.wikimedia.org/wiki/Performance/Runbook/Arc_Lamp_service
[2] https://www.mediawiki.org/wiki/Excimer
[3]
https://techblog.wikimedia.org/2014/12/29/how-we-made-editing-wikipedia-twice-as-fast/
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