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nice'd processes ruin performance

asked 2012-08-28 13:52:25 -0600

fa2k gravatar image

Hi, I'm running some simulation tasks which take about 100 hours. When using the computer while 4 tasks are running, it is noticeably slower. I have 4 cores (real cores, not hyperthreading), I have set the nice level of the tasks to 19, and I have plenty of free memory. The tasks don't produce a lot of I/O, much less than 1 MB/s. When using a separate multithreaded application, it does not use all of the CPU as I would expect, it uses about 1 core (monitored in htop) and the rest is used by the long simulation processes. From what I understand, processes with lower nice value should always run before processes with higher nice value, so why isn't that happening? (it's even lagging behind as I write this text)

-Marius (also, the Login/signup to post button didn't respond when I clicked it)

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answered 2012-08-28 22:38:23 -0600

FranciscoD_ gravatar image

Well, nice is a little more complex than simply "running processes with less nice values before ones with more nice values". http://en.wikipedia.org/wiki/Nice_(Unix) explains it a little.

If you want your simulation to use preassigned cores, you can use "taskset"

man taskset # for more info
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Asked: 2012-08-28 13:52:25 -0600

Seen: 74 times

Last updated: Aug 28 '12