Performance/Triage

{{message/box|If you have any feedback/suggestions/questions regarding the performance triage process, you can share them in #perf-triage, or reach out to Dave Hunt or Frank Doty.

Nomination

Bugzilla

To (re)nominate a bug for triage, set the Performance Impact flag in Bugzilla to ?

This can be found by clicking Show Advanced Fields followed by Set bug flags when entering a new bug:

Or by expanding the Tracking section when editing an existing bug:

GitHub

To nominate a bug for triage, add the Performance label to an issue. This can be done by filing an new issue with the "Performance issue" template:

Or by opening an existing issue on GitHub and selecting the label from the right-hand bar:

Currently, only the following GitHub repositories are supported:

• fenix
• android-components
• focus-android

Queries

Performance triage

Full Query

ID	Summary	Status
1771902	Compositor CSS animations are not paused in fully occluded windows	NEW
1777875	Lenovo Privacy Guard with "Enable this feature when typing passwords" causing excessive UI responsiveness delays (jank)	NEW
1931717	[meta] High OOM rate and CC time in YouTube	NEW
1941716	On a fresh profile, Negative heap-unclassified on "My Bugs" query on b.m.o	NEW
1959837	openstreetmap iD editor - slow zooming	NEW
1966492	JS isn't minified in Fenix release builds	NEW
1988776	MutationObserver's getReceiverFor is slow when there are a lot of observers	NEW
1994817	Firefox CPU usage spikes to 100%+ on some sites, particularly when opening new tabs	UNCONFIRMED
2002795	Horrible new tab bar	REOPENED
2008927	Choppy/stuttering scrolling with touchpad	UNCONFIRMED

10 Total; 10 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Performance triage (pending needinfo)

Full Query

ID	Summary	Status
1939354	RAM too much	UNCONFIRMED
1943419	Fluidd memory leak	UNCONFIRMED
1946913	Consume too much memory	UNCONFIRMED
1988608	Tabs in Firefox refresh when multitasking	UNCONFIRMED
1993778	Firefox causes MacBook battery to drain fast	UNCONFIRMED
1994231	Search with bookmark keywords doesn't work when browser's lagging	UNCONFIRMED
2008564	UI freezes on long React/DOM sessions despite moderate CPU usage (main-thread JS long tasks)	UNCONFIRMED

7 Total; 7 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Recently opened bugs with performance keywords in the summary

Full Query

ID	Summary	Status
2013232	Enabling JS Execution Tracing (tracing) in profiler disables native frames and memory tracing	NEW
2013404	shader-f16 failing to render in WebGPU	NEW
2013634	Firefox fails WPT /css/css-view-transitions/capture-with-offscreen-child-translated.html	NEW
2013655	Add SimpleURLPattern component for faster compression dictionary use	NEW
2013721	Highlight text selection is slow/inconsistent when Windows 11 taskbar is hidden.	ASSIGNED
2013749	Testcase creating N empty text nodes is 380x slower in Nightly.	NEW
2013750	Testcase creating N empty textnodes and then appending them in bulk is 60x slower in Firefox	NEW
2013766	Firefox seems to have memory leaks when watching YouTube lives	UNCONFIRMED
2013886	Opening about:support janks the parent process for 600ms getting WebGL info	NEW
2013937	firefox memory leak when minimised	UNCONFIRMED
2013986	Refactor variations of nsLayoutUtils::IsAncestorFrame	NEW
2014160	Cache2 I/O thread 100% CPU due to O(n) linear search in CacheIndexIterator::RemoveRecord with large cache	UNCONFIRMED
2014262	Surface 'Translate' option higher in menu when selecting foreign text	NEW
2014280	RTC.IceConnectionStateChange callbacks can be slow	NEW
2014284	Remove leading slash from NewTabAttributionService endpoint variable	NEW
2014367	[Sample] Bug used as sample for testing file bug functionality in Perfherder	NEW
2014418	Clear SharedSubResourceCache on memory pressure?	ASSIGNED
2014454	Minor but annoying bug in translation triggering. Prompted to translate a JSON API consisting of almost entirely numbers into norwegian.	NEW
2014525	CPU goes to 100%, OffscreenCanvasRenderingContext2D.fillText is calling gfxFontGroup::EnsureFontList & gfxFontGroup::AddFamilyToFontList on every call.	UNCONFIRMED
2014620	When the translation panel appears and I click the "Not now" button, when I refresh the site, this panel is no longer displayed.	NEW
2014639	Autocad Web crashes in firefox if webGPU is enabled.	NEW
2014677	Google Slides rendering unusably slow	UNCONFIRMED
2014840	Reduce memory allocations for filling simple paths (PathBuilder ops vector, Path)	NEW
2014930	./mach lint -l android-fenix is slow (runs heavy Gradle tasks / build steps)	NEW
2014947	Firefox uses excessive memory and freezes entire laptop	UNCONFIRMED
2014989	Prototype DOM Tree Translation API	NEW
2014998	WebGPU error in Construct 3 on macOS	UNCONFIRMED
2015006	Testcase creating Map keys is 4x slower, and iterating them is 2x slower	NEW
2015040	Add Performance tests for security layer	ASSIGNED
2015083	Text size cannot be increased for Firefox-translations	NEW
2015166	Drawing a WebGPU canvas to a 2D canvas does a readback	NEW
2015175	Improve Memory summary verbosity and detail inclusion	NEW
2015256	Testcases with json operations are 10x-2x slower in Firefox	NEW
2015295	The "Translate Selection" dialog needs a "Replace button"	NEW
2015300	[wpt-sync] Sync PR 57640 - Don't divide by zero on perfect matches	NEW
2015308	Modified codepen demo (https://codepen.io/robbobfrh84/pen/qBZJbYz?editors=0010) is much slower in Firefox	NEW
2015309	Modified codepen demo (https://codepen.io/shubniggurath/pen/RNaWvdm?editors=0010) is slower in Firefox	NEW
2015312	memory leak in nsCocoaWindow.mm PopupWindow shadowParameters	ASSIGNED
2015313	potential memory leak in nsCocoaWindow.mm acceptsFirstMouse	ASSIGNED
2015334	memory leak in Cocoa widget touchbar support	ASSIGNED
2015337	potential memory leaks in Cocoa widgets text input handling	ASSIGNED
2015355	fillRect with createLinearGradient becomes much slower after many iterations	UNCONFIRMED
2015358	Battery API doesn't exist	UNCONFIRMED
2015364	potential out of bounds write in GPU data arrays on macOS	ASSIGNED
2015370	Link previews becomes stuck with constant high CPU usage until process killed	UNCONFIRMED
2015414	[Gemini translation] I am using Firefox Android Beta, and it shows that I am logged in; however, the app crashes when I click "Sign Out."	UNCONFIRMED
2015473	Expose additional network timings to TRR performance tests	NEW
2015508	Improve Gemini and Qwen's memories retrieval performance	NEW
2015513	Include a performance tests for ml security layer allow path	ASSIGNED
2015602	Significant performance issue with complex SVG at blowfish.page	UNCONFIRMED
2015693	Update WebGPU CTS to new version eb9091d141e126fd9479a62aeceb927b73b6af47 from 2026-02-06 06:03:53	ASSIGNED
2015700	Neither about:translations's source text area nor target language selector focused on page load	NEW
2015727	Quick action for Translate appears even for words that don’t match exactly	NEW
2015734	Translation boxes are not responsive and stack vertically when the window height is reduced	NEW
2015794	The l-beam cursor should not be displayed in the translation box	NEW
2015796	Ensure reference target observers are removed from labeled descendants of nearest ancestor label in nsLabeledNodeList	UNCONFIRMED
2015839	100% CPU usage when playing youtube video, all cores used - windows 11	UNCONFIRMED
2015887	llama.cpp leaks ~500mb for each link preview performed until threads are exhausted	NEW
2015935	Adding Adaptive Performance Prefs to Nimbus Manifest	ASSIGNED
2015955	Large event jank from synchronous decoding of images in Kotlin-wasm application	NEW
2015988	Firefox using too much memory	UNCONFIRMED
2016103	Refactor CommonPerformPromiseCombinator to isolate iterator-specific logic	ASSIGNED
2016129	[Linux] NTP scrolls up and down fast with productivity widgets enabled and lower vertical view for Firefox window	NEW
2016239	Memory leak: Compose SharedElement animation retains destroyed HomeActivity and HomeFragment via InputMethodManager → Recomposer → snapshotInvalidations	NEW
2016281	Finish responsiveness work on sidebar	NEW
2016304	in the search bar the space bar doesnt work unless i press it twice slowly the it puts a single space	UNCONFIRMED

66 Total; 66 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Triage process

Introduction

The goal of performance triage is to identify the extent to which bugs impact the performance of our products, and to move these bugs towards an actionable state. The goal is not to diagnose or fix bugs during triage. We triage bugs that have been nominated for triage and bugs in the Core::Performance component that do not have the performance impact project flag set.

During triage we may do any/all of the following:

• Request further information from the reporter (such as a profile)
• Set the performance impact project flag
• Add performance keywords
• Move the bug to a more appropriate component

Who is responsible for triage?

Everyone is welcome to take part in triage. By default, everyone on the performance team is enrolled in triage rotation, but we also have participants from outside the team.

How do I schedule a triage meeting?

If you are on triage duty, you will receive an invitation as a reminder to schedule the triage meeting on the shared performance calendar with the nominated sheriffs invited at a time that works for them. The responsibility of scheduling the meeting falls to the lead sheriff. Once a triage meeting has been scheduled, it’s a good idea to remove the reminder event from the calendar to avoid confusion. It’s a good idea to use the shared calendar, as this increases the visibility of the performance triage and allows other members of the team to contribute or observe the process.

What if a sheriff is unavailable?

The rotation script is not perfect, and doesn’t know when people are on PTO or otherwise unavailable. If the lead sheriff is available, it is their responsibility to either schedule the triage with the remaining available sheriff or to identify a suitable substitute for the unavailable sheriff(s). If the lead sheriff is unavailable, this responsibility passes onto the remaining available sheriffs.

How do I run a triage meeting?

The following describes the triage process to follow during the meeting:

1. Ask if others would prefer you to share your screen. This can be especially helpful for those new to triage.
2. Open the first triage query to show bugs nominated for triage or in the Core::Performance component without the performance impact project flag set. The bugs are sorted from oldest to newest. For each bug in the list, follow these steps:
   • Bugs that look like tasks that were filed by members of the Performance team will generally need to be moved to the Core::Performance Engineering component.
   • For defects: Determine if the bug is reproducible and actionable. If not, add a needinfo for the reporter asking for more information and move onto the next bug. We have a template that you can modify as needed.
   • For all bugs (including enhancements):
     • Set the performance impact project flag.
     • Add the appropriate performance keywords.
     • Move the bug to the correct Bugzilla component.
3. Open the second triage query to show bugs that have open needinfo requests. The bugs are sorted from oldest to newest. For each bug in the list, follow these steps:
   • If the needinfo was set less than 2 weeks ago, move onto the next bug.
   • If the needinfo was set more than 2 weeks ago but less than 2 months ago, consider adding a needinfo for either: another reporter of the issue, someone with access to the appropriate platform(s) to attempt to reproduce the issue, or a relevant subject matter expert.
   • If the open needinfo was set more than 2 months ago, close the bug as inactive. You can modify the inactive bug template as needed.
4. If time permits, open the third triage query to show recently opened bugs with performance related keywords in the summary. If any of these look like performance bugs, they can either be triaged the same way as bugs in the initial query or they can be nominated for triage in a subsequent meeting.

What if things don't go as expected?

Don't panic! The triage process is not expected to be perfect, and can improve with your feedback. Maybe the result of the triage calculator doesn't feel right, or you find a scenario that's not covered in these guidelines. In this case we recommend that you bring it up in #perf-triage, or consider scheduling a short meeting with some triage leads (you can see some recent leads in the triage rotation). If in doubt, leave a comment on the bug with your thoughts and move on. There's a chance someone will respond, but if not the next performance triage sheriffs may have some other ideas.

How do I determine the performance impact project flag?

The performance impact project flag is used to indicate a bug’s relationship to the performance of our products. It can be applied to all bugs, and not only defects. The triage calculator should be used to help determine the most appropriate value for this flag. In addition to setting the performance impact project flag, make sure to use the “Copy Bugzilla Comment” button and paste this as a comment on the bug.

For more information about what this flag, and it's settings mean see this blog post.

How do I determine the performance keywords?

There are several performance related keywords, which can be helpful to understand how our performance issues are distributed, or whenever there’s a concerted effort to improve a particular aspect of our products. The triage calculator may recommend keywords to set, and by typing “perf:” in the keywords field in Bugzilla, you will see the available options. Select all that apply to the bug.

How do I determine the correct Bugzilla component?

Ideally we would only have bugs in the Core::Performance component that are the responsibility of the engineers in the performance team. For performance bugs to have the best chance of being fixed, it's important to assign them to the correct component. In some cases the correct component will be obvious from the bug summary, description, or steps to reproduce. In other cases, you may need to do a bit more work to identify the component. For example, if there's a profile associated with the bug, you could see where the majority of time is being spent using the category annotations.

How do I read a performance profile?

It's useful to be able to understand a profile generated by the Firefox Profiler, and hopefully someone in the triage meeting will be able to help. If you find an interesting profile, or just want to understand how to use them to analyse a performance problem, we encourage you to post a link to the profile (or bug) in #joy-of-profiling where someone will be happy to help. The profile may even be analysed during one of the regular "Joy of Profiling" open sessions that can be found on the Performance Office Hours calendar.

Triage calculator

The Performance Impact Calculator was developed to assist in identifying and applying the performance impact project flag and performance keywords consistently. If you have feedback or would like to suggest changes to this tool, please share these in the #perf-triage Matrix channel.

Triage rotation

The sheriffs are allocated on a weekly basis, which is published here. The rotation is generated by this script.

Templates

New bug

This template is included in the description for new bugs opened in the Core::Performance component. If a bug is opened in another component and then moved to Core::Performance, this template can be used as needed to request additional information from the reporter.

### Basic information

Steps to Reproduce:


Expected Results:


Actual Results:


---

### Performance recording (profile)

Profile URL:
(If this report is about slow performance or high CPU usage, please capture a performance profile by following the instructions at https://profiler.firefox.com/. Then upload the profile and insert the link here.)

#### System configuration:

OS version:
GPU model:
Number of cores: 
Amount of memory (RAM): 

### More information

Please consider attaching the following information after filing this bug, if relevant:

 - Screenshot / screen recording
 - Anonymized about:memory dump, for issues with memory usage
 - Troubleshooting information: Go to about:support, click "Copy text to clipboard", paste it to a file, save it, and attach the file here.

---

Thanks so much for your help.

Moved to Core::Performance

This bug was moved into the Performance component. Reporter, could you make sure the following information is on this bug?

 - For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/ , upload it and share the link here.
 - For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
 - Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

Thank you.

No longer able to reproduce

This bug doesn’t seem to happen anymore in current versions of Firefox. Please reopen or file a new bug if you see it again.

No response from reporter

With no answer from the reporter, we don’t have enough data to reproduce and/or fix this issue. Please reopen or file a new bug with more information if you see it again.

Expected behaviour

This is expected behavior. Please reopen or file a new bug if you think otherwise.

Website issue

According to the investigation, this is a website issue. Please reopen or file a new bug if you think otherwise.