Performance/Triage

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
1939354	RAM too much	UNCONFIRMED
1941716	On a fresh profile, Negative heap-unclassified on "My Bugs" query on b.m.o	NEW
1943419	Fluidd memory leak	UNCONFIRMED
1946913	Consume too much memory	UNCONFIRMED
1959837	openstreetmap iD editor - slow zooming	NEW
1966492	JS isn't minified in Fenix release builds	NEW
1988608	Tabs in Firefox refresh when multitasking	UNCONFIRMED
1988776	MutationObserver's getReceiverFor is slow when there are a lot of observers	NEW
1993778	Firefox causes MacBook battery to drain fast	UNCONFIRMED
1994817	Firefox CPU usage spikes to 100%+ on some sites, particularly when opening new tabs	UNCONFIRMED
2002795	Horrible new tab bar	REOPENED
2002920	Drag-and-drop 5MB of text on an blank tab leads to recurring 4.5s jank on the parent-process, spending time in nsIURIFixup.getFixupURIInfo	ASSIGNED
2008564	UI freezes on long React/DOM sessions despite moderate CPU usage (main-thread JS long tasks)	UNCONFIRMED

16 Total; 16 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Performance triage (pending-needinfo)

Full Query

ID	Summary	Status
1940206	Garbage collection is less efficient on macOS(ARM) than on Linux(x86)	UNCONFIRMED
1960195	Dual monitor (laptop / Monitor) browsing very slow refresh in second monitor	UNCONFIRMED
1961523	Firefox constantly freezes	UNCONFIRMED
1964744	high cpu memory youtube	UNCONFIRMED
1968418	Closing a long-running twitch tab hangs browser for minute(s) (GC in recvConduitClosed of Conduit)	NEW
1977599	Embedded video file playback hitching and freezing browser.	UNCONFIRMED
1981274	utter-disappointment-with-firefox-performance	UNCONFIRMED
1982631	Google Maps takes forever to load	UNCONFIRMED

8 Total; 8 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Recently opened bugs with performance keywords in the summary

Full Query

ID	Summary	Status
2008506	[BSD] firefox exits with a segmentation fault in headless mode in freebsd cause of having no X-server and gpu	UNCONFIRMED
2008529	Automation test has significant performance drop in Firefox 140 and 144	UNCONFIRMED
2008560	Investigate JS IPDL serialization performance	NEW
2008705	WebGPU: external textures missing on Linux	NEW
2008706	WebGPU: external textures missing on Android	NEW
2008734	Do not reject the promise returned by `navigator.gpu.requestAdapter()`	ASSIGNED
2008779	Memory leak in AboutFragment after onDestroyView via RecyclerView adapter listener	ASSIGNED
2008851	Intermittent random flashing rectangles in the Slack web page's blue background when using SWGL	NEW
2008886	[HDR/Windows] Implement zero-copy fast path for P010 format	NEW
2008904	Investigate options of persisting arbitrary data in memory	NEW
2008960	Remove pref for MITIGATION_EXTENSION_POINT_DISABLE in Windows GPU process sandbox	NEW
2009020	Add Translations to AI Controls	NEW
2009062	memory leaks and freezing	UNCONFIRMED
2009130	WebGPU should not be using the static gfx blocklist	NEW
2009295	Cache Storage API cache.match() operations exhibit O(n) performance degradation causing severe slowdowns as cache size grows	ASSIGNED
2009306	Benchmark from bug 2009295 (https://ylngxt.csb.app/) is 3x slower in Firefox to write the first 5000 URLs to cache	NEW
2009372	Fenix: DoH performance shows high latency when resolving multiple hostnames in parallel (bis)	NEW
2009394	Consider implementing faster date conversion algorithm	NEW
2009402	[Experiment] The “Updated sidebar coming soon” callout message is dismissed by the Translate door hanger when navigating to a website in a foreign language	NEW
2009506	[WebGPU] [aarch64] [arm64] @ dri2_allocate_textures	UNCONFIRMED
2009606	[wayland] vsync with frame callbacks causes high CPU load and works badly with VRR	NEW
2009633	Clean up unnecessary logic in TranslationMenuItem	NEW
2009639	Modified Codepen demo is 1.5x slower than Chrome, getting slightly slower as iterations increase. Looks to be time spent in JSON serailization.	NEW
2009763	Memory leak in HomeFragment – CoordinatorLayout retained after onDestroyView()	NEW
2009834	[Linux/Firefox Nightly - Vertical Tabs] Excessively high CPU Usage when mousing into collapsed vertical tabs.	UNCONFIRMED
2009871	Enable WebGPU on Android Nightly	NEW
2009894	The DocumentFragment counterexample benchmark on MDN has rapid runaway memory with Firefox.	NEW
2010059	Resolve memory leaks in TabbedBrowsingTest#verifyCloseAllPrivateTabsNotificationTest	NEW
2010062	Add message length threshold before generating memory from conversation	NEW
2010069	Localize remove this memory label	NEW
2010070	Enable GPU support for onnx-native	NEW
2010079	Surprisingly high CPU usage in GMP process telemetry	NEW
2010087	Firefox uses FAR too much memory	UNCONFIRMED
2010135	[fluent-dom] While translating an element with fluent ID "newtab-topsites-add-shortcut-label" a child element of type "br" was removed.	NEW
2010287	Perfspewer write overhead too high when writing to jitdump files	NEW
2010336	Perfspewer with IONPERF=src has too much overhead	NEW
2010353	Assertion failure: !mFinishedBuildingColumns (Should only call once!), at /builds/worker/checkouts/gecko/layout/generic/ColumnSetWrapperFrame.cpp:107	NEW
2010399	Consider Adding Favicon and Address Bar Treatment to about:translations	NEW
2010402	memory.grow is not correctly implemented for custom page sizes	ASSIGNED
2010414	Prototype static memory protection	NEW
2010569	`background-clip: text` applied element loses background when moved with `transform: translate()`	UNCONFIRMED
2010582	Slowing down then crashing	UNCONFIRMED
2010615	Compression dictionaries URLPattern parsing slow on shopify	NEW
2010617	fast memory leak on macOS, no extensions	UNCONFIRMED
2010633	Perma browser/extensions/newtab/test/xpcshell/test_WallpaperFeed.js | test_Wallpaper_protocolURI - [test_Wallpaper_protocolURI : 242] Should dispatch WALLPAPERS_CUSTOM_SET with moz-newtab-wallpaper:// URI - when Gecko 148 merges to release on 2026-02-16	NEW
2010672	Collect WGPU Adapter information	NEW
2010683	Memory 17GB+	UNCONFIRMED
2010819	[perf] Add fast path for callers that check PendingQueueLength() == 0	NEW
2010922	Make TranslationsParent Conform to AIFeature	NEW
2010993	Make Translations UI States Reactive to Changes in Feature Enabledness	NEW
2011001	Translation of open websites in the background no longer works	UNCONFIRMED
2011051	sign(-1.0) in webgpu/wgsl returns nonsense in Firefox on Windows	UNCONFIRMED
2011061	Firefox process not freeeing memory properly	UNCONFIRMED
2011080	Testcase adding N attributes to range-sliders is 3x-4x slower than Chrome. Both the browsers are quadratic, Firefox is more quadratic.	NEW
2011082	WebGPU on Apple Silicon causes system-wide video/animation stutter	UNCONFIRMED

55 Total; 55 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.