RAM usage on 8GB MBP

[dhdb]

Recently I upgraded the RAM on my mid 2010 15" MBP Core i5 2.4 GHz (first mac, still running Snow Leopard for now) from 4 to 8 GB, which gave a nice performance boost to Photoshop and multitasking in general. (I use a lot of Photoshop, InDesign, Illustrator, Vectorworks and some Office)
Every now and then i took a look at the System Memory tab in Activity Monitor, and here I noticed some behavior I don't understand. See for example the screenshot attached.

It lists more than 4,05 GB of Active Memory, yet the Real Mem of all currently visible processes add up to approximately 1135 MB… As you can see (well, not really) the rest of the processes down the list certainly do not make up for the other 3 GB of Active memory. I thought the Active memory category only measured memory that is actually being used? Could someone please explain how this works on the mac?
I have seen this behavior quite a few times now and I'm wondering what's going on. I do not remember that when I still had 4 GB of RAM, the active memory would be up this high with almost no programs running…

 

[seong]

Definitely weird. I dunno why, but I would consider updating to Lion if yo duo not have any problem with not being able to use PPC apps anymore. I upgraded from 2GB to 8GB, and it was well worth the money.

 

[palpatine]

i have 8gb. i will try to pay more attention, but to be honest, i am kind of lazy

i don't plan to upgrade to lion, and so i disagree with the previous poster. adobe, in particular, seems to have issues. i like lion (played with it in the store today), but don't plan to upgrade for a few weeks. i want all of the major ugliness worked out by guinea pigs

See this site for more.
http://kb2.adobe.com/cps/905/cpsid_90508.html

 

[dhdb]

Thanks for the replies. I'll probably wait with upgrading to Lion until the .1 update, but isn't that beside the point? Is there any new RAM management in Lion?
palpatine, do you think this is caused by Adobe software? Can it leave huge amounts of RAM occupied after all its processes have quitted? That seems like a serious flaw!?