I use Firefox to run very specific tasks and one of the reasons it's not my main browser is it's large memory consumption. It starts at 60.000 K but easily climbs up to 490.000 K - after only 5 minutes - combined with plugin-container.exe (146+342 respectively). It's also consuming 31% of the CPU. After another few minutes everything runs very slowly in Firefox and I have to close and open again.
Is this normal? Can I reduce the RAM consumption and CPU usage in any way?
You did not specify your OS, but looking at your past questions, I'm assuming Windows.
You should look Palemoon project. http://www.palemoon.org/
Mozilla does not provide optimized browser packages for Windows, meaning you may be losing speed and efficiency when you use your browser; and truth be told, most people use their browsers all the time! That needs to change, so, here is the Pale Moon project: Custom-built and optimized Firefox browsers for Windows Operating Systems. Make sure to get the most speed and efficiency out of your browser!
By far the biggest factor in memory consumption is the websites you surf + extensions you install. Many extensions out there are just flat out poorly written. While their efforts are commendable, they continued improvements as they get popular can be appalling.
The majority of resource usage by Firefox isn't used by the core Firefox functions but by the sites opened in Firefox. So whether the resource usage you list is reasonable or not depends entirely on you "very specific task" and without knowing what it is it is impossible to judge.
That said there are a few things that can cause Firefox to use excessive resources because of a damaged profile or a buggy add-on. You can try launching firefox with the -P switch to launch the profile manger and create a new profile. Then try doing your "very specific task" in the clean profile and see if the resource usage of Firefox is lower.
Another thing to look at is newer versions of Firefox. Mozilla has a MemShrink project going on to reduce the resource usage of Firefox. The first improvements are available Firefox 7 Beta, and further improvements are available in Firefox 8 Aurora and Firefox 9 Nightlies. They will be buggy, though, but they probably could do your "very specific task" with lower resource usage.
I'm not able to provide a direct solution, but a common cause for the crazy memory usage is because of Flash video. I don't know what your "very specific tasks" are, but usually the two biggest contributors to Firefox's inefficient memory usage is running and loading many Youtube videos back to back (such as a playlist) or viewing a Flash-based stream (such as justin.tv or ustream.tv) for an extended period of time.
If you're doing the latter, my only suggestion is to use Chrome while using Firefox for your other tasks. For the former, the only thing I can think of is to be conscious of how many videos you go through and to remember to exit out of Firefox after a bit to "reset" its memory usage. I know it's a hassle, but until that MemShrink project addresses these issues, it's the most simple and straightforward way to combat the memory usage.
