1716156 - Computer's Network Connection Slowed when Firefox is Running

Status: RESOLVED WORKSFORME

(Core :: Networking, defect, P2)

Description

[Michael]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:89.0) Gecko/20100101 Firefox/89.0

Steps to reproduce:

I pay for 400Mbps cable internet service and usually get that amount (+-100Mbps) depending on time of day. It's usually pretty stable.

I opened Firefox on Windows 10 Pro, gigabit network adapter, 16GB RAM, SSD. Ran speedtest.net and fast.com to check internet performance. I could rarely get more than 100Mbps from either site.

Had a Spectrum technician come to the house yesterday to check the connection. He did some repairs to improve the signal quality coming into the cable modem.

I could get expected speeds when using a mobile device, but each time I tried Firefox on the PC, it was between 70-120Mbps, consistently.

Having plenty of time to try things, I refreshed the computer.

After the installation of Windows, I tried the speed tests using Edge (Chromium) and was able to achieve speeds of 300-700Mpbs. This is well within the range of expected performance.

I installed Firefox and checked the speed of those two sites. Again, the performance was slow. I may have gotten 170-200Mbps a few times, but usually got speeds of ~100Mbps.

I opened Edge along side of Firefox and both browsers reported slow speeds.

I closed Firefox. Then, Edge would report speeds back in the 300-500 Mbps range.

These tests were performed with a new Cat6 cable connected to either the router, or cable modem directly. Tests were repeated several times with similar results.

WIndows 10.0.19043
16GB RAM, 512GB SSD
HP EliteDesk 705 G2 SFF
AMD PRO A4-8350B R5
Broadcom NetXtreme Gigabit Ethernet Plus (1.0 Gbps connection reported in network properties)

Actual results:

Network traffic with other apps is affected when Firefox is running. When Firefox is not running, other network-related apps work as expected.

Expected results:

Firefox should not affect network performance.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Networking' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[(inactive) Nihanth Subramanya [:nhnt11]]

Thanks for reporting. Do you have any extensions installed? Have you checked whether this happens even when using a new profile?

A http log might be helpful to diagnose this - please not it may contain sensitive information, so you may want to create the log on a new profile.

Comment 3

[Michael]

Thank you for asking. I should have included in my bug report that I ran Firefox in both normal mode and Troubleshooting mode with plugins disabled. The issue occurred in both modes.

I will check this issue with a new profile and log it. I should be able to do this tomorrow.

This afternoon, I reset Windows again, fully wiping the drive, and reinstalled my software.

This evening, I was running Beyond Compare to sync (via SFTP) our web server with my local computer. I had Firefox running when I started the file comparison. The comparison was much slower than usual.

I then closed Firefox and opened another instance of Beyond Compare. The first instance continued file transfers at a slower pace. The second instance, however, was much quicker, like I am used to seeing.

Then, with Firefox still closed, I refreshed the first instance of Beyond Compare. The speed was back to normal.

It appears that while it's running, Firefox affects any connections that are opened after Firefox starts. Connections that remain open, even after Firefox closes, continue at a slower pace. However, connections that are opened after Firefox closes, work as fast as usual.

The extensions I have installed are:
ACTIVE
Bitwarden
ColorZilla
Snap Links
uBlock Origin
Uppity
Web Developer

DISABLED
Facebook Container
LastPass
New Tab Override

Thank you for looking into this.

Comment 4

[Michael]

Attachment: 1 -child.1816.moz_log

Comment 5

[Michael]

Attachment: 2 -main.2108.moz_log

Comment 6

[Michael]

Attachment: 3 -main.8832.moz_log

Comment 7

[Michael]

I created a new profile in Firefox and ran a couple set of tests. However, the first tests were not logged because I forgot to click "Start Logging". However, the results are similar to when I did enable logging.

400Mbps up/20Mpbs down is what I pay for. Upload performance does not appear to be affected.

Values below are (Mbps down/Mbps up).

Here is the first set of tests without logging. All tests used fast.com. Firefox used the new profile.

Edge and Firefox closed.
Opened Firefox.
(69/25) FIREFOX
Opened Edge. Firefox still open.
(60/21) EDGE
Closed Firefox. Edge still open.
(340/22) EDGE
Opened Firefox. Edge still open.
(200/21) EDGE
(150/26) FIREFOX
(240/20) EDGE
Closed Firefox. Edge still open.
(390/21) EDGE

Here is the second set of test with logging. All tests used fast.com. Firefox used the new profile.

Edge and Firefox closed.
Opened Edge.
(380/23) EDGE
Opened Firefox. Edge still open.
(240/23) EDGE
(130/25) FIREFOX
Closed Edge. Firefox still open.
(140/22) FIREFOX
Opened Edge.
(250/21) EDGE
Closed Firefox. Edge still open.
(310/23) EDGE
Opened Firefox. Edge still open.
(180/21) EDGE

Comment 8

[Kershaw Chang [:kershaw]]

See bug 1503704. There is a high CPU usage problem with fast.com, so maybe this is the reason that Firefox affects other applications.

Comment 9

[Michael]

Thank you for the reply. I can understand that, however, during my testing, I opened Firefox, did not do anything with Firefox other than open it, then I ran the test in Edge. Therefore, that bug should not relate to this issue.

I am at work now, but I will try this again tonight or Friday when I'm back at home.

Comment 10

[Tsgpc Help]

Thanks for your idea for more information visit our website https://tsgpchelp.com/

Comment 11

[Bas Schouten (:bas.schouten)]

I can't locally see any impact from having Firefox on my download speeds elsewhere. I'm easily able to reach 1Gb down in other applications while running Firefox.

Could you include a profile?
See http://profiler.firefox.com/, please upload and put the link in here.

Comment 12

[Michael]

A lot has changed since I submitted this issue. I now have 1Gb internet and a very fast computer. I'm not able to test with the same conditions as two years ago.

Thanks!

Comment 13

[Mayank Bansal]

Based on Comment 12