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
1940667	30s of jank on parent-process doing something around getFixupURIInfo and ContentAreaDropListener.sys.mjs (resource://gre/modules/URIFixup.sys.mjs:278:18)	NEW
1941716	On a fresh profile, Negative heap-unclassified on "My Bugs" query on b.m.o	NEW
1942031	Bad canvas performance on this example (nokiadesignarchive.aalto.fi)	NEW
1943419	Fluidd memory leak	UNCONFIRMED
1943503	High CPU usage on Debian x64 bookworm (VMware player guest)	UNCONFIRMED
1945665	airbnb.com - Attempting to enter a destination in the search by using the gboard causes the gboard to become unresponsive	NEW
1946248	Too much time spent in gfxMacPlatformFontList::DeprecatedFamilyIsAvailable during startup	NEW
1946913	Consume too much memory	UNCONFIRMED
1950901	Testcase generating N=5K forms (using credential mgmt API?) takes 30s in parent-process and 50s in content process. Chrome takes 9s.	NEW
1955509	Constant CPU usage while idle on the Tiki.org website front page	UNCONFIRMED
1957692	Testcase generating N=500 forms and submitting them takes 27s in both parent and content processes,and is 675x slower than Chrome (Part2 of bug 1950901)	NEW
1958712	Testcase generating N <META> elements is 20x slower than Chrome and does weird stuff in Compositor and SceneBuilder (PAPZCTreeManager::Msg_UpdateZoomConstraints)	NEW
1959837	openstreetmap iD editor - slow zooming	NEW
1964744	high cpu memory youtube	UNCONFIRMED
1965718	Google Maps framedrops when I'm panning the map	UNCONFIRMED
1966492	JS isn't minified in Fenix release builds	NEW
1967585	Excessive memory allocation when toolbar icons are updated (e.g., during downloads or extension changes) — sometimes triggers OOM killer	UNCONFIRMED
1972941	[Linux] File downloading is CPU-intensive	NEW
1975272	Animated newtab background images consume CPU even when not in the foreground	NEW
1982980	Memory leak in Firefox on Android when repeatedly appending and removing an iframe	UNCONFIRMED
1988608	Tabs in Firefox refresh when multitasking	UNCONFIRMED
1988762	Slow scrolling performance on particular sites (mastodon)	NEW
1988776	MutationObserver's getReceiverFor is slow when there are a lot of observers	NEW
1993778	Got a new Mac (new to the OS) and noticed only with Firefox does battery drain rapidly, used Firefox Profiler (below) to see if anything stuck out but didn't see anything, any help appreciated	UNCONFIRMED

28 Total; 28 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Performance triage (pending-needinfo)

Full Query

ID	Summary	Status
1882916	Firefox consumes a lot of CPU and makes me Mac M2 hang for a good 15 seconds	UNCONFIRMED
1940206	Garbage collection is less efficient on macOS(ARM) than on Linux(x86)	UNCONFIRMED
1956931	High CPU usage after clicking buttons on at least one site	UNCONFIRMED
1960195	Dual monitor (laptop / Monitor) browsing very slow refresh in second monitor	UNCONFIRMED
1961523	Firefox constantly freezes	UNCONFIRMED
1963933	Google search results in high CPU usage and spike in temps. Happens with most of the browsers but Firefox results in higher temps spikes and CPU usage	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

11 Total; 11 Open (100%); 0 Resolved (0%); 0 Verified (0%);

Recently opened bugs with performance keywords in the summary

Full Query

ID	Summary	Status
1993587	YouTube videos won't play under high CPU load (like when building Firefox in the background)	NEW
1993838	WebRender becomes blurry on complex pages at high resolution (5120x1440) with NVIDIA eGPU on Linux (X11)	UNCONFIRMED
1993839	Claude AI Web: Text streaming response causes CPU thread to spike to 100% usage	UNCONFIRMED
1993971	poor audio/video performance using Google Meet with Firefox 142	UNCONFIRMED
1994014	nsLayoutUtils::GetPopupFrameForPoint returns the popup even when hovering over its shadow.	ASSIGNED
1994071	WebRender GPU blocked / disabled on Fedora 43	UNCONFIRMED
1994150	opening browser creates an outofmemoryerror report after crashing	UNCONFIRMED
1994203	SharedMemory{Mapping,Handle} needs a Rust API	NEW
1994206	Translation feature is not available on some devices	NEW
1994314	Fenix: DoH performance shows high latency when resolving multiple hostnames in parallel	ASSIGNED
1994346	In fragmented context, perform a second reflow for abspos frame, or push it	NEW
1994431	Firefox is nearly unusable on a busy system (pages won't load if CPU is used heavily)	UNCONFIRMED
1994482	Remove session.perf.visibility_event_rcvd_ts @backward-compat shim	NEW
1994549	Firefox unable to load pages or make network requests when other processes are using high CPU on Mac	UNCONFIRMED
1994885	[wpt-sync] Sync PR 55498 - Add WEB_FEATURES.yml for wasm core memory features	NEW
1994902	Firefox uses a 2000MB+ memory with 6 tabs open.	UNCONFIRMED
1994907	With "JavaScript" feature enabled on the profiler, testcase from bug 1935829, the browser does 3 5-second long GCs without reducing memory. Manually reducing memory takes 36 seconds without reducing memory.	NEW
1994984	Increase GPU process launch timeout	ASSIGNED
1995046	Add perf test for query intent detection	ASSIGNED
1995066	WebGPU CTS regression on Windows: webgpu:api,operation,command_buffer,image_copy:offsets_and_sizes:*	NEW
1995163	[wpt-sync] Sync PR 55531 - Mark element-render-blocking-* slow	NEW
1995180	remove some extra rect creation when calling nsLayoutUtils::RoundGfxRectToAppRect	NEW
1995181	Measuring the memory of a 1GB Blob takes 3 seconds (from about:memory) spending time in shaCompress and SHA_ROTL. Maybe it can be faster?	NEW
1995222	Opening a Chromium issue list is slower in Firefox compared to Chrome	NEW
1995247	Nonsensical default translation direction	NEW
1995265	Massive memory/resource leak in DirectX-using code	UNCONFIRMED
1995281	perf issue: Whole document is serialized when context menu is opened (by buildAskChatMenu via addPageContext)	NEW
1995379	backdrop-filter: blur() severely impacts performance when applied to New Tab card backgrounds	NEW
1995551	[composable toolbar] Performing two consecutive voice searches replaces the first search term with the second one	NEW
1995565	Testcase creating Uint8Array from wasm memory is 2.5x slower in Firefox.	NEW
1995626	from Base64/Hex are slower than chrome	ASSIGNED
1995634	Utilize nsIDocumentEncoder for Translations Language Identification	NEW
1995803	Assertion failure: sf && sf->PresShell() && !sf->PresShell()->IsResolutionUpdated(), at /builds/worker/checkouts/gecko/layout/base/nsLayoutUtils.cpp:783	NEW
1995866	Update browser_ml_semantic_history_search_perf.js to static embeddings	NEW
1995927	Game-of-life demo optimized by chatgpt is 5x slower in Firefox	NEW
1995983	Put bytecode response to in-memory cache	NEW
1995994	Fix memory vs disk cache handling in InstantiateClassicScriptFromCachedStencil	ASSIGNED
1996007	[wpt-sync] Sync PR 55618 - Fix incorrect link to slow-style-change.py iFix incorrect link to slow-style-change.py in update-on-style-change.htmln update-on-style-change.…	NEW
1996009	[LNA] Most strings in the prompt are not translated in Arabic	NEW
1996058	Assertion failure: std::isnan(aSize) || aSize >= 0, at /builds/worker/checkouts/gecko/layout/base/nsLayoutUtils.cpp:1689	NEW
1996080	Assertion failure: std::isnan(aSize) || aSize >= 0, at /builds/worker/checkouts/gecko/layout/base/nsLayoutUtils.cpp:1691	NEW

41 Total; 41 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, set the performance impact project flag to pending-needinfo, and then 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 are waiting further information to determine the performance impact. The bugs are sorted from oldest to newest. For each bug in the list, follow these steps:
   • If the performance impact project flag was set to pending-needinfo less than 2 weeks ago, move onto the next bug.
   • If the performance impact project flag was set to pending-needinfo 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 performance impact project flag was set to pending-needinfo 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.

If you do not have enough information to set the performance impact project flag, open a needinfo request against an appropriate individual (such as a reporter), and set the performance impact project flag to pending-needinfo.

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.