Multi-process Firefox will use up to 20% more RAM initially
Running multi-process Firefox on PC‘s will increase between 10% to 20% initially on average according to a memory test Mozilla ran recently. Firefox is planning to deploy multi-process capability to the stable channel in Firefox 46 slated for release on April 19, 2016.
Ghacks notes that Mozilla’s Electrolysis “e10s” project which brings multi-process to users will be released with Firefox 46 Stable release.
According to test results gathered by Mozilla Platform Engineer Eric Rahm, users can expect Firefox to consume more memory under multi-process enabled versions of Firefox.
This seems like a fair tradeoff for potential security and performance benefits, but as we try to grow the number of content processes we’ll need to take another look at where that memory is being used.
Through the years, Mozilla has tried to control Firefox’s rampant use of memory through features like MemShrink, which slashed memory utilization by as much as 50 percent. However, if one goes by the recent tests, Mozilla’s effort to control RAM usage will come to naught if it enables  multi-process browsing in Firefox.
