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Why does top show 730MB of RAM used, but the "Task Manager" shows 190MB?

Some more information on my system:

  • Lubuntu 14.04
  • VirtualBox

Screenshots:

top in terminal

Task Manager

Community
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Rahmani
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  • Depends on how you count the memory, bytes or bits , see http://www.translatorscafe.com/cafe/units-converter/data-storage/calculator/megabit-to-megabyte/ . And then there are the buffers See http://www.linuxatemyram.com/ . Your two tools are showing the same information using different measures, top is a little more detailed. You can also use free -m – Panther May 17 '14 at 15:11
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    @NGRhodes related, not duplicated. – Braiam May 17 '14 at 17:28

2 Answers2

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Because it includes cache and buffers in top (you can see them as individual items to the right of the total memory).

NGRhodes
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I believe i found the answer:

To understand the process architecture of VirtualBox see The VirtualBox architecture :

<p>Once you start a virtual machine (VM) from the GUI, you have two
windows (the main window and the VM), but three processes running.
Looking at your system from Task Manager (on Windows) or some system
monitor (on Linux), you will see these:</p>

  1. VirtualBox, the GUI for the main window;

  2. Another VirtualBox process that was started with the -startvm parameter, which means that its GUI process acts as a shell for a VM;

  3. VBoxSVC, the service mentioned above, which is running in the background to keep track of all the processes involved.

This was automatically started by the first GUI process.

The source with more information.

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user279450
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    Could you please clarify how this is relevant? The OP is presumably showing the top output of the guest OS, and anyway what you show has nothing to do with memory usage, only with the number of processes launched by virtualbox. – terdon May 17 '14 at 15:23
  • @user279450 do you mean if I install lubuntu on a real machine, those numbers will be the same? But I don't understand the relevance. – Rahmani May 17 '14 at 15:28
  • well, it seems i am wrong. What i thought was because you have your normal processes(windows) and you add more in virtualbox, your windows will read it's own and virtualbox has some extra in it's own environment. Maybe misthinking of me, maybe a language barrier. Thats why you are here ;) – user279450 May 17 '14 at 15:35