memory usage in firefox and gecko

Update: If you got here because you just read an article about this issue, maybe you should just go read Stuart’s most recent post instead of this one.

For a long time there have been a lot of complaints about the memory usage in Firefox and anything else that used the Gecko engine. And looking at the numbers for what Firefox would use for memory, they seemed valid. But on the other side of the story, I know that the Mozilla team has been pretty diligent about fixing memory leak bugs. Allocations are tracked closely across checkins and leaks are fixed when they are discovered. So why the different perceptions for what people were seeing in the field and what the programmers were tracking during a development cycle?

As Mozilla starts down the path to running in the mobile space we are spending time looking at memory pressure issues more closely. Stuart and Vlad spent time looking at the behavior of the allocator during some simple tests and it sounds like the early data suggests that Mozilla really doesn’t leak that much memory at all. But it does thrash the allocator pretty hard and that’s what causes the perception of memory leaks. There’s a lot more information in Stuart’s post of course, including some good visualizations.

Over the next few months it will be very interesting to see what happens with both memory usage and perceived performance especially as we connect those numbers to a successful mobile strategy. I’m sure Stuart will continue to post updates as he goes along and as tools become available to be able to spread this work out to others. For those who are trying to use the engine from Firefox in a mobile device (like the Nokia N810, for example) this work will be very useful. Go Stuart!