Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!jaap+ From: jaap+@andrew.cmu.edu (Jaap Akkerhuis) Newsgroups: comp.unix.questions Subject: Re: Nicer than nice! Message-ID: Date: 6 Feb 90 17:12:00 GMT References: <9400@cat.UUCP> <1990Feb5.052345.2120@iwarp.intel.com> <707@umvlsi.ecs.umass.edu>, <90Feb5.165122est.5069@neat.cs.toronto.edu> Organization: Information Technology Center, Carnegie Mellon, Pittsburgh, PA Lines: 31 In-Reply-To: <90Feb5.165122est.5069@neat.cs.toronto.edu> Excerpts from netnews.comp.unix.questions: 5-Feb-90 Re: Nicer than nice! Jean-Francois Lamy@cs.ut (1522) > someone wrote: > >> Is there a possibility to change the priority of a process more than a > >> 'nice -19' would do? I would like be able to start programs in background > to which Randal Schwartz replied: > >>the scheduler. There isn't anything in off-the-shelf UNIX that tags the > >>process as "don't run this unless nobody else is doing much of anything." > and Uday Hegde confuses matters by saying: > >process with that nice value [-19] runs only when nothing else in the system > >wants to. > >Correct me if I wrong. > Indeed. The scheduler uses niceness as one of many factors in determining > priority. In *practice*, several maximally niced jobs can still impact > significantly the system performance. Recent SunOS releases seem especially > prone to this behaviour (I will dispense you from my pet theories on the topic > because I'd like to check them with the source first, should we *ever* receive > it). UNIX Edition 7 had the same problem. If I remember correctly, it was caused by the fact that the swapper swapped anything in which hadn't be in for a while and then the scheduler deciced it was a real nice process, so it was swapped out again before being run. So processes which were supposed to soak up only idle time still had an impact on the system. jaap