The memory usage is ever increasing when downloading.

I was downloading the Doom 3 demo which is about 450MB. I opened the Activity Monitor and noticed that the RAM-used is ever increasing. Once I finished downloading it, I only had 700MB free RAM. (before downloading, I had 1.1 GB free)

Why?

Anyone noticed this issue?

But that memory gets free again, no? So why bother?
The system uses memory all the time, whatever it is doing (for example caching a download stream).

As long as your system continues to run smoothly (which it definitely is with 700MB of free RAM!) there's absolutely no need to worry about memory usage.

Avalon said:

But that memory gets free again, no? So why bother?

Click to expand...

No, it didn't. I noticed that first when I was downloading the XCode 2.1 from apple. Only 300MB RAM was free once the XCode was downloaded and mounted. Scary? no?

AlexN said:

No, it didn't. I noticed that first when I was downloading the XCode 2.1 from apple. Only 300MB RAM was free once the XCode was downloaded and mounted. Scary? no?

Click to expand...

Well, you just said it, the disk image was mounted. As it is a virtual disk, and in the case of Xcode 2.1 quite a big one, that's pretty normal.
Virtual disks are mounted into memory, and take up memory as long as they are mounted.

Avalon said:

Well, you just said it, the disk image was mounted. As it is a virtual disk, and in the case of Xcode 2.1 quite a big one, that's pretty normal.
Virtual disks are mounted into memory, and take up memory as long as they are mounted.

Click to expand...

Oh, so .dmg files are mounted into memory? What if I only had 512MB RAM? I couldn't mount any files that are larger than 512MB?

No it would just rely more on virtual memory

trpnmonkey41 said:

No it would just rely more on virtual memory

Click to expand...

Exactly.

Okay, just to make it clear. When there is enough physical memory, the .dmg file will be mounted into it? If it is, that's really cool.

Wouldn't it be cool if one day, there weren't harddisk anyone, anything could fit into memory? Say, 500 GB of RAM? haha, some dreams...

AlexN said:

Only 300MB RAM was free once the XCode was downloaded and mounted. Scary? no?

Click to expand...

Not really, 300MBs is still a fair amount of ram. and if you needed more for another app, OS X would allocate it to it.

Okay, this is what I've discovered so far. It has nothing to do with the files being .dmg or not, virtural disk image doesn't mount in physical memory.

No matter what kind of files you download, whether the browser is Safari or Firefox, the memory is ever decreasing. Try downloading a 500MB+ video file, it's the same.

It's a bug, I can expect this be fixed in 10.4.3.

It's not a bug. When downloading the incomplete parts of the file are stored in the RAM because they have to assembled together when the download is complete and stored on the hard drive

trpnmonkey41 said:

It's not a bug. When downloading the incomplete parts of the file are stored in the RAM because they have to assembled together when the download is complete and stored on the hard drive

Click to expand...

Okay, but once the download is complete, the memory should be freed, no?

It will be put into the Inactive category, which means that Safari will have priority but it is essentially free

trpnmonkey41 said:

It will be put into the Inactive category, which means that Safari will have priority but it is essentially free

Click to expand...

Hmm...but the Activity Monitor says the memory left is only 300MB, and the GarageBand is much slower. Reset the computer, and it goes back to normal.

If it says 300mb is left then there is no reason for GarageBand to be much slower. And of course a restart will make things quicker because it flushes everything out of the memory