Does memory usage scale up based on amount of installed memory?

[dland512]

I have an iMac (2.4 GHz Intel Core 2 Duo) with 4 GB 800 MHz DDR2 SDRAM installed. I just got a Mac mini (2.3 GHz Core i5) with 8 GB 1333 MHz DDR3 RAM installed.

I have noticed as I'm using the new mini that it seems to be allocating a greater amount of memory making the overall percentage used about the same between the systems. Basically the mini is using roughly twice as much memory as I would have expected. I looked into it and sure enough, many of the processes seem to reflect this. Here are some examples taken just after starting up the box:

task....................iMac.........mini
kernel_task..........251 MB.....494 MB
WindowServer......24 MB.......60 MB
Activity Monitor.....29 MB......59 MB

I also attached screenshots of the activity monitor for both systems.

What's the deal with this? Do these processes ask for more memory based on how much is available in the system?

 

[The-Pro]

Well if more memory is available the system (kernel_task) will use more. This is because its loads more data into the RAM so that the system has quicker access to more, frequently used, data. It so that the OS feels smoother.
When the 4GB is installed then the system will use less in order to leave the user more memory.

Also, i dont know if you are running lion, SL or Leopard on your iMac, but Lion uses substantially more memory then the older OSX versions. So if you are not running lion on your iMac then that could also be a reason for the difference.

 

[dland512]

Well if more memory is available the system (kernel_task) will use more. This is because its loads more data into the RAM so that the system has quicker access to more, frequently used, data. It so that the OS feels smoother.
When the 4GB is installed then the system will use less in order to leave the user more memory.

Also, i dont know if you are running lion, SL or Leopard on your iMac, but Lion uses substantially more memory then the older OSX versions. So if you are not running lion on your iMac then that could also be a reason for the difference.

Sorry, I should have included that both systems are running Lion.

The kernel task alone doesn't account for the entire discrepancy between the systems, though I suppose the other processes could be doing the same thing. I mean as long as it doesn't adversely affect the performance of the box I don't really care that much, but it just seemed a little odd.

 

[The-Pro]

Sorry, I should have included that both systems are running Lion.

The kernel task alone doesn't account for the entire discrepancy between the systems, though I suppose the other processes could be doing the same thing. I mean as long as it doesn't adversely affect the performance of the box I don't really care that much, but it just seemed a little odd.

No it doesn't, I just talked about that because it is the biggest process. It is that way yes, most processes will use more RAM so that the overall performance of your system is better. Window server," it acts as a server process to composite/draw windows onto the screen. It deals with taking the bitmap of each window and drawing it to the correct location on screen (as an OpenGL texture these days), layering the windows correctly and compositing them where there are translucent areas (again all done in OpenGL these days). It also handles the double buffering of windows backing stores allowing the updates to the window content to be smooth and flicker free." (originally posted by robbieduncan in another thread) When you trigger mission control, change spaces and all that, the RAM usage of window server will increase so that next time everything is smooth.
I noticed the same as you when I upgraded to more RAM. Important thing to know it just the bit in bold. When I had increased RAM in my systems I was amazed at how much smoother everything feels.

 

[GGJstudios]

What's the deal with this? Do these processes ask for more memory based on how much is available in the system?

You really don't have to worry about how RAM is allocated or used. Mac OS X does a good job of managing memory, without interference or involvement from the user or 3rd party software. It's going to use whatever RAM is available.

 

[leman]

I completely agree with what GGJstudios said. In addition, I can recommend you to completely disregard any RAM usage statistics as long as you are happy with the performance of your computer. These statistics are only useful when your PC is running slow and you want to find the cause.

Now, if you are interested in the technical part, than: yes, OS X wil try to utilize all available RAM by using it for all kinds of things like caches etc. Also, it is less likely to page out background applications. AFAIK, it also does special optimizations like preallocating RAM for new processes so that they can start faster. These are all good things. Remember: idle RAM is basically wasted RAM and occupied RAM is well-utilized RAM as long as it is used to make your computer faster.

 

[Harkinian]

The kernel_task process seems to use almost exactly proportionally more RAM if you have more. That is, if you have 1GB then upgrade to 4GB, it uses 4X as much RAM. Other processes use more but not proportionately more. But can anyone confirm this?

 

[simsaladimbamba]

The kernel_task process seems to use almost exactly proportionally more RAM if you have more. That is, if you have 1GB then upgrade to 4GB, it uses 4X as much RAM. Other processes use more but not proportionately more. But can anyone confirm this?

kernel_task uses 1,52 GB on my 32 GB machine, that is almost 5% of RAM capacity. I do not care, as RAM is there to be used.

 

[xraydoc]

Free RAM is wasted RAM.

The system will use your available RAM to keep more things accessible - faster than re-reading over again from the HDD.

If a newly launched app requires more than is free, the system will release cache from other apps to make space for it.

In other words, it's appropriately using more RAM to make your computer faster.

 

[Harkinian]

kernel_task uses 1,52 GB on my 32 GB machine, that is almost 5% of RAM capacity. I do not care, as RAM is there to be used.

Unless you're reporting a different memory usage number than I am (I was going off RSIZE), that busts my myth. 1.0GB on my friend's computer with 12GB of RAM, not proportional.

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Free RAM is wasted RAM.

The system will use your available RAM to keep more things accessible - faster than re-reading over again from the HDD.

If a newly launched app requires more than is free, the system will release cache from other apps to make space for it.

In other words, it's appropriately using more RAM to make your computer faster.

It does help your system sometimes, but free RAM isn't always wasted RAM. There are cases where Mac OS X doesn't manage the memory properly. For example, VMWare Fusion 4 somehow rarely causes problems where the inactive RAM takes over the free RAM but never gets freed when needed unless you manually purge, causing a massive system slowdown.