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Background: I have 16 GB of memory in my machine.

When my machine uses already 15 GB of memory and my application allocates another chunk of 2 GB memory I run out of physical memory and swapping (should) pops in and uses the available disk-space. Instead Windows freezes completley. Why does this happen? I thought Windows (a user-process) does never page out memory related processes/threads/os-memory. Why does it block then?

I would expect that my process hangs but why does it happen with the entire OS? One idea: It's related to the memory-size of 2 GB which blocks the internal memory management until it succeeded. Therefore the other processes block as well. I am not sure if this makes any sense. What are your thoughts on this?

  • I'm not at all sure what's going on. Is your hard drive crashing? Or out of space? Or just whatever programs you're running keep crashing? – Xen2050 Jan 2 '15 at 19:32
  • Have you switched off auto windows memory management? Do you have a swap file? Does Windows think it's located elsewhere? – Optichip Jan 2 '15 at 19:57
  • In my machine I use a fusion drive with almost 200 GB free hard-drive space. The drive is working without any problems. I am wondering whats causing this because I can reproduce this on several machines with different configurations in several offices. FYI: The system doesn't crash - it simply freezes. The OS is running with default settings in the memory management. – HelloWorld Jan 2 '15 at 20:47
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I am assuming that Windows is able to use the page file (it is not disabled and there is space left in the page file) and by freezing you mean it takes nearly forever to show reaction like minutes.

If Windows is under memory pressure (not enough RAM), it starts swapping out data from RAM to the harddisk/page file. The exact algorithm what data is swapped out is very complex but in general it is the least recently used memory which is not locked from swapping (some kernel pages and hard disk drivers and so on are locked). It can even swap out parts of explorer.exe and some other important GUI processes or firewall/antivirus. When you try to interact with the GUI it has to load it back from the harddisk, which is very slow compared to RAM and I have seen cases, where it takes more than 15 minutes to at least partly unfreeze the desktop.

If you want to further investigate, I recommend using the performance monitor. In Windows 8 you can access it with taskmanager->performance->ressource monitor but it it is also usable in older windows systems. In Windows 8 you can even see which process and which file the culprit is.

  • Thanks for this answer. How to deal with the fact that even the resource monitor might freeze? In the last case I restarted the machine after two hours of no response - so I should give it even more time to (eventually) to come back? – HelloWorld Jan 3 '15 at 2:44
  • Which OS are you using? Also looking into the eventmanager might help because 2 hours seem extremly long except maybe the machine is under heavy load the whole time. There you might find an other reason for freezing instead of slow harddrive swapping like disk read/write errors or windows services failing, in short everything red and sometimes yellow. You might also try to lower the priority of your process in the taskmanager or from inside your process. By freezing do you mean reacting extremly slow, completely frozen or frozen but the mouse movable? – sweet home Jan 3 '15 at 9:23
  • I am on Windows 7 but I can also reproduce this on several other machines with Windows 8. With freeze I mean a complete freeze (audio stops playing, mouse doesn't move anymore). As mentioned, also profilers do not work anymore so its hard for me to determine whats causing this issue when the profilers dont even update their view. I don't know if the machine would ever come back though. – HelloWorld Jan 3 '15 at 16:46
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After reading the Q and comments, I think I can answer...

That's just the way every other Windows computer works, from what you've said.

Your answer would be... "Hard drives are slow"

  • I do agree, but why do processes like the explorer are swapped out as well? I know, it's a user-process but still wondering. – HelloWorld Jan 2 '15 at 22:47

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