CS4 64 version using 5.6 gigs memory w no open photos

Question

Hi, I just upgraded recently to a Dell computer running Vista 64 and with 8 gigs memory and thought that would be enough for Photoshop. I worked today for about 2 hours opening raw scenery files in Bridge and making heavy use of the adjustment brush in camera and heavy use of other camera raw tools. Each file that was brought into Photoshop was further modified there and then closed.
When I went to open another file, I was told it could not be done because of a lack of memory. Photoshop was using 5.6 gigs of RAM. Bridge was using another 0.5 gig.
Photoshop is set (left default setting established by Photoshop) to use scratch space on drive C which because I just started with this computer a few days ago has about 500 gigs of free contiguous space. But actually I don't to make much use of scratch space because such use would slow computer down.
Does the 64 bit version just keep taking more and more RAM without releasing any after a file is closed? I gave computer several minutes wait to see if Photoshop would release memory--nope.
Everything ran fine until that error, machine did not slow down at all.
Its annoying to have to close Photoshop because it doesn't release memory.
Are other people finding that the program fails to release memory?

Answer 1

I am not sure about "or at the request of the OS". I used to write OS kernel and MM code. If an app has blocks of heap, it may or may not relinquish it depending on how it is written. The garbage collection daemon rarely has the option to force block release. Most common exceptions are the algorithms for deadlock. MM can force paging, but performance goes through the floor. In CS4, PS maps its tile management scheme onto a 3D model. PS wants blocks to be contiguous for performance. This scheme is already failing. As images get much bigger over the next few years, it will break-down completely. There is a thread where users are experiencing PS allocating 12GB of RAM and then not releasing it upon closing documents. This code architecture was fine when folks shot 8MP cameras. Now it is 21MP, next year 45MP will be released. I regularly do panas at 1.2GB. This architecture will not survive much longer. PS must learn to deal with memory management or folks will simply not use it. Aperature is already gaining market share.
H