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When I start memory-intense processes (such as git gc in a repository with huge files), Linux starts becoming unresponsive after some time, at first the UI lags a little, then the mouse stops moving and then the keyboard stops working too. The interesting thing about it that it apparantly also disables the SysRQ keys for some reason, I can't use SysRQ-Kill or SysRQ-Reboot anymore in that state.

What can I do in order to prevent this situation from happening, maybe like letting Linux kill processes that use too much memory.

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    You can't access to the terminal with ctrl-alt-F3? – Sepahrad Salour Dec 6 '13 at 17:07
  • @SepahradSalour: No, neither that. (And it would be strange if that worked but SysRQ not.) – heinrich5991 Dec 6 '13 at 17:09
  • And the CPU usage remains normal? – goldilocks Dec 6 '13 at 17:33
  • @heinrich: Many times this happened for me but ctrl-alt-F3 work well in centos... – Sepahrad Salour Dec 6 '13 at 17:53
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Linux by default already has a "OOM killer". When your system runs out of memory, the kernel will kill a process, trying to chooses whichever one is the culprit in the system running out of memory. However, if your system is configured to use a swap, this won't happen until it runs out of both main memory and swap space. If your swap device is slow (e.g. a spinning hard disk) this might not happen until well after your system has slowed to a crawl and become unresponsive.

You can try turning off your swap, and see if this results in your memory-hungry process being killed before your system becomes unusable.

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Assuming you have an adquate amount of memory and all of your hardware is working as intended, try messing around with ulimit.

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Actually, I think if you wait a bit, your keystrokes would work, but short of that, you might run jobs like this at a much lower priority.

As root, before the memory utilization spikes, renice the priority. It is important to remember that positive number have a lower priority, and negative one higher. See how things work if you renice the process to +10 or even +20.

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    He is talking about MEMORY usage not CPU which you have mentioned nice command! – Sepahrad Salour Dec 6 '13 at 17:56

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