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cyildiz
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Joined: 13 Dec 2009
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 Posted: Sun Oct 09, 2011 12:00 am Post subject: How to kill a process that is using all CPU |
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Hi,
I've recently had this problem few times in my AMD64 Gentoo PC.
1) I had a python script running and plotting with matplotlib. Because of my fault, it was trying to plot a lot(!) of points. When it started making the plot, PC got stuck.
2) I wanted to open a txt file with vim. Later, I realized that the file was 2GB (due to continuous flow of debugging output of a program). Again computer got stuck.
In both cases PC was not actually stuck, but I couldn't do anything. Whole CPU power was being used. I did ctrl+alt+F1 with a huge lag. But I never even manage to log in to kill the programs that cause the problem. Finally I had to reboot both times.
In this cases what should I do? Is there a way to limit CPU usage of programs, to reserve some for killing them at least? |
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Hypnos
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| Posted: Sun Oct 09, 2011 12:35 am Post subject: |
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First on your second question, if you are using bash, consider the ulimit command. To find out how to use it, type
Now, to your first question. it is useful to have the "magic sysrq" key option enabled in your kernel. You can read more about it in
| Code: | | /usr/src/linux/Documentation/sysrq.txt |
For this application, sysrq+k can be used to kill everything on the current console, useful for killing your X session and all daughter process. Also, sysrq+s then sysrq+u then sysrq+b can be used to reboot more safely than just holding down the power button.
There is a nice Wikipedia page about it.
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Jaglover
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Hypnos
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| Posted: Sun Oct 09, 2011 1:15 am Post subject: |
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| Jaglover wrote: | | In fact, when it comes to X apps xkill does real good job. While success of kill command depends on whether the program is listening or not xkill just terminates the client. |
Only if the window manager or a virtual terminal can be manipulated by the user in order to invoke xkill ... this is doubtful if you can't even switch to a text console.
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Jaglover
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| Posted: Sun Oct 09, 2011 1:22 am Post subject: |
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Right ... | Quote: | | I did ctrl+alt+F1 with a huge lag. But I never even manage to log in to kill the programs that cause the problem. Finally I had to reboot both times. |
but usually you get some delayed response, as OP stated.
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cyildiz
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Joined: 13 Dec 2009
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| Posted: Tue Oct 11, 2011 7:41 am Post subject: sysrq for a single process |
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Hi, thanks for all replies.
ulimit seems nice, I should try it.
I did not know sysrq either, it may be useful.
But my main problem is that, I want to kill the cpu eating process and continue working.
Would it be possible to add a new key combination that gets the highest cpu using process and kills it? This would be great. I looked up in the internet but did not come across such thing. |
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Hypnos
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| Posted: Tue Oct 11, 2011 7:46 am Post subject: Re: sysrq for a single process |
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| cyildiz wrote: | But my main problem is that, I want to kill the cpu eating process and continue working.
Would it be possible to add a new key combination that gets the highest cpu using process and kills it? This would be great. I looked up in the internet but did not come across such thing. |
I don't know of one either. If it just runs in a terminal (i.e., no GUI), you can run it on a non-X console. Then you can switch to that console and use SysRq-k to kill that process (and all the other processes on that console).
EDIT: You might somehow get monit to do what you want (in Portage).
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ppurka
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| Posted: Tue Oct 11, 2011 8:22 am Post subject: Re: How to kill a process that is using all CPU |
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| cyildiz wrote: | Hi,
I've recently had this problem few times in my AMD64 Gentoo PC.
1) I had a python script running and plotting with matplotlib. Because of my fault, it was trying to plot a lot(!) of points. When it started making the plot, PC got stuck. |
Try to place some limits on the oom killer. The modifications can be done to /etc/sysctl.conf and can be applied to the live system by running sysctl -p after you have done the modifications. The configuration options you would want to look at are: | Code: | vm.overcommit_ratio
vm.overcommit_memory |
The latter is probably better left unset. However, it should be set to 2 if you want to be very strict about restricting memory usage. This option restricts the total Virtual Memory size to the restrictions set above. For any program it comes up under the VIRT column when you look at top. Look at the documentation in /usr/src/linux/Documentation for the meaning of these parameters. I don't remember the exact file, but if you grep for overcommit_ratio you should be able to locate the file.
| Quote: | | 2) I wanted to open a txt file with vim. Later, I realized that the file was 2GB (due to continuous flow of debugging output of a program). Again computer got stuck. |
I am pretty sure by "stuck" it was actually heavily swapping. I have never seen a Linux system lock up because it was taking too much cpu. In this case, you could try Alt-SysRq-f to kill the process that is taking the most memory.
In the case of vim, use vim -n if you are opening a huge file. This is to prevent vim from trying to create a .swp backup file. This backup file creation is the one which eats up memory and cpu. Alternatively, use less to view huge files.
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