Firefox, Thunderbird Lagging? Lag Fix Inside

For the last days I have experienced lags and issues both in the Firefox web browser and the Thunderbird email client. With Thunderbird, I experienced lag that resulted in the Thunderbird window not responding for some time.

The window of the email program recovered after some time, so that I could access the program's functionality again.

With Firefox it is another issue. The browser just stops receiving traffic from the Internet as if it is blocked by a firewall or as if the Internet connection died. The only solution here so far was to restart the web browser.

David Bradley discovered a solution that fixed the Thunderbird lag issue, and probably the Firefox no traffic issue as well.

David mentioned frequent stutter or lag in the browser leading to the "not responding" message that can last for a few moments. This was the same behavior that I experienced in Thunderbird.

Fix lags in Thunderbird

The solution or fix here is to assign one specific core to the Firefox, or in my case Thunderbird, process. This obviously only works if a multi-core cpu is available.

Users who just want to test the setting can assign a specific core by opening the Windows Task Manager with Ctrl-Shift-Esc, right-clicking the firefox.exe or thunderbird.exe process and selecting Affinity from the context menu.

There they need to select a specific cpu core or remove one from the listing to test the fix. Please note that this is only a temporary solution. A system state change, e.g. a reboot, standby or hibernation resets the affinity settings that you have selected.

A permanent solution is to create a new program shortcut and set the cpu affinity this way.

The command for Firefox is this one:

C:\Windows\System32\cmd.exe /c start "C:\Program Files\Mozilla Firefox\" /affinity x firefox.exe

where x is the cpu core number. (cpu 0 = 1, cpu 1 = 2, cpu 2 = 4, cpu 3 = 8 and so on).

For Thunderbird the command is

C:\Windows\System32\cmd.exe /c start "C:\Program Files (x86)\Miramar 3.3 Alpha 1\thunderbird.exe" /affinity x thunderbird.exe

The easiest way is to copy the shortcut from the start menu or to use Windows Explorer to open the folder where the program is installed. There you can right-click firefox.exe or thunderbird.exe and select to create a new shortcut.

It is likely that we will see an official fix in the coming days / weeks. You can then simply delete the shortcut or modify it again so that all cpu cores are used by the application. It is unlikely that this change has an effect on the program's performance.

Windows XP users cannot make use of the command. The suggestion here is to use the freeware RunFirst which sets the process affinity automatically to one core.

Has this fixed your issue as well? Let me know in the comments. (thanks David, via)

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