Does CPU scheduler favor root?

michal017 · 10-14-2009, 09:35 AM

Does Linux CPU scheduler favor processes running under root to processes running under non-superuser? The nice value is the same.
I can't find this information anywhere, however a test with my application tells me otherwise - in case of a high load I see problems of processes running under regular user, the ones running under root seem to be fine. Thanks.

kakaka · 10-14-2009, 07:29 PM

The nice *offset* is the same, or the resultant priority is the same?

nigelc · 10-14-2009, 11:15 PM

I don't think it makes any difference who or what the user is.

michal017 · 10-15-2009, 01:58 AM

kakaka: if by nice *offset* you mean the value set by e.g. nice -n, then yes.. the resultant priority, as seen by e.g. 'top' could be different though
nigelc: yes, that's my conclusion as well by searching the web on this subject

michal017 · 10-15-2009, 09:56 AM

I see, that the priority, as shown in the PR column of top's output is 15 for processes running under root and 18 for processes running under regular user. The processes in question are almost identical, so I'm wondering why is there the priority difference.

nigelc · 10-16-2009, 12:05 AM

The priority does change every now and then. Do a top then "r" re-nice a few and see what happens.