CyberTech

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Mozilla is working on a new so-called Process Priority Manager that could debut in Firefox 69 in order to improve the performance of active tabs.

Basically, what the company wants to do is develop a method of directing some of the resources used by background tabs to the active tab that someone is using at a specific time.

This way, Mozilla thinks, the overall performance of the browser could be much improved, as Windows would technically provide the foreground tab with all the resources it needs to render the content on the loaded page, regardless of type.

Already enabled in Nightly
However, as Mozilla engineers themselves note in a post on Bugzilla (via TechDows), the new Process Priority Manager isn’t generating the major boost in performance that the team expected when starting the project.

“According to our Beta experiment, the process priority manager had no measurable impact on page load time, tab switch time, or user retention. So, the good news is that it doesn't appear to make things worse. However, I'm a bit sad to say that it also didn't appear to make things better (via the probes that we measure),’ Mozilla Firefox front-end engineer Mike Conley explains.

“We do know, however, that lowering background tab process priority allows the OS to prioritize work in foreground tabs. So at the very least, this should be a resource usage win.”
The new feature won’t use the resources allocated to media tabs, as Mozilla wants sites like YouTube to continue running in the background without any interruption. As a result, background media processes will be ignored to keep playback untouched.

The Process Priority Manager is already enabled in the latest Firefox Nightly version, and it should be part of Firefox 69 projected to go live on September 3 this year.
 

Local Host

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The new feature won’t use the resources allocated to media tabs, as Mozilla wants sites like YouTube to continue running in the background without any interruption. As a result, background media processes will be ignored to keep playback untouched.
So the biggest offenders to performance won't be using the feature (understandable for people that run media in the background), however this turned into a useless feature with no benefits like stated,
However, I'm a bit sad to say that it also didn't appear to make things better
Is at times like this I think people at Firefox are like this,