Re: [SLUG] nice and priority on top- thank you Ian

From: Patrick \(at work\) (pwgrant@cssi-fl.com)
Date: Wed May 01 2002 - 14:24:15 EDT


Someone buy him a pizza.
----- Original Message -----
From: "Mikes work account" <mrock@stewartsigns.com>
To: <slug@nks.net>
Sent: Wednesday, May 01, 2002 2:00 PM
Subject: RE: [SLUG] nice and priority on top- thank you Ian

>
> I received a few explanations that were very good but I believe yours was
> the most complete and easy to understand. I have passed your explanation
on
> to others here to read. A superb explanation.
>
> Michael C. Rock
>
>
> -----Original Message-----
> From: slug@lists.nks.net [mailto:slug@lists.nks.net]On Behalf Of Timothy
> Sent: Wednesday, May 01, 2002 11:40 AM
> To: slug@nks.net
> Subject: Re: [SLUG] nice and priority on top
>
>
> This is one of those explanations about Unix/Linux the ordinary user
> dreams of. A, pardon the expression, "nice" clear cut explanation in
> ordinary understandable language. Bravo!
>
> Timothy
>
> *********** REPLY SEPARATOR ***********
>
> On 5/1/2002 at 10:41 AM Ian C. Blenke wrote:
>
> >On Wed, 2002-05-01 at 10:05, Mikes work account wrote:
> >>
> >> Can someone explain the difference between the nice value and the
> >priority
> >> value on the top program. When I change the nice value to 19 to
> reduce
> >the
> >> impace of a process on system performance then the priority goes up
> to
> >19 as
> >> well. Should I change the priority to a lesser value or should it
> do it
> >on
> >> its own when I up the nice value??
> >>
> >> Michael C. Rock
> >
> >This is a function of the scheduler.
> >
> >The process priority is dynamic and constantly changing.
> >The nice value of a process is generally static, although you can
> >"renice" a running process as often as you wish.
> >
> >The lower the priority of a process, the more likely it is to be run.
> >
> >The nice value is added to the priority of a process to adjust its
> >importance. A positive nice value will make a process less important.
> A
> >negative nice value will make a process more important.
> >
> >The nice value is just a basis for the priority. The scheduler changes
> >the priority of a process while it is running. If a process is
> resource
> >intensive, its priority will drop in the scheduler (the priority
> number
> >will grow as it is penalized for using resources) to allow other
> >processes with lower priority to run.
> >
> >Think of the nice value as a "priority baseline". As a process gets
> more
> >time to run, its priority number will grow to the point where it
> exceeds
> >the priority of other jobs on the system with lower priorities. Once
> the
> >lower priority processes have had their chance.
> >
> >Process priority is based on a number of factors aside from simple
> >aging, however. CPU use, memory use, IO wait time, and dozens of other
> >factors go in to recomputing the constantly changing priorities of
> >processes on your system. This is what the scheduler does. Changing
> the
> >behavior of the scheduler can change the entire "feel" of your
> computer
> >(making it more/less interactive, or running long-running compute jobs
> >more/less efficiently).
> >
> >Giving a positive nice value will penalize a process so that it will
> >always schedule last after everything else has a chance to run.
> >
> >Giving a negative nice value will give a process preference over other
> >running processes on the system. The more negative the nice value, the
> >less likely other jobs will be given a chance to run.
> >
> >To answer your question though, yes the system should update the
> >priority to start at the niceness value you set. In fact, it should
> >generally never drop below the nice value - at least with the current
> >scheduler, AFAIK.
> >
> >- Ian C. Blenke <icblenke@nks.net> <ian@blenke.com>
> >http://ian.blenke.com
>
>
>
>



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