Is it normal that a user can take down the whole system by using too much memory?

[Frank Leonhardt]

On 2018-06-04 10:43, Steve O'Hara-Smith wrote:
> On Sat, 02 Jun 2018 19:25:31 -0400
> Brennan Vincent <brennan at umanwizard.com> wrote:
> 
>> Thanks John for the response -- this should help me solve my practical
>> needs.
>> 
>> I'm also curious, however, to learn more from an OS design 
>> perspective.
> 
> 	Best way to do that is look at the code.
> 
>> Why isn't it possible for the kernel to realize it should kill 
>> `eatmem`
>> rather than make the system unusable?
> 
> 	The code in vm_pageout.c that handles out of swap conditions tries
> to kill the biggest process - by that it means the one estimated to 
> release
> the most memory. To that end it skips processes in various states - 
> killed,
> protected, system, non-running and then picks the biggest of the 
> remaining
> processes to kill.
> 
> 	One thing that may cause the random chaos you see is that killing a
> process takes time, especially if that process has swapped out pages, 
> if
> something else calls for memory it has finished dying then the next 
> biggest
> process will get killed even though the process responsible has already
> been killed (after all it might be locked up and failing to die).

You might want to look at this:

http://blog.frankleonhardt.com/2011/large-swap-files-on-freebsd-die-with-mystery-killed-howto-add-lots-of-swap-space/

Regards, Frank.