Problem with nice

[doelz at urz.unibas.ch]

In article <9008072224.AA21964 at chaos.ocean.fsu.edu>, steve at CHAOS.OCEAN.FSU.EDU (Steve Van Gorder) writes:
> 
> I was under the impression from previous discussions in this news group
> and from reading the manuals that if I type  "npri -h 250 -p pid" as superuser
> then this process would be assigned a "non-degrading" priority of 250. 

correct.

> According to schedctl(2) man page this means that it is of lower priority than
> all other processes and shouldn't interfere with ANY interactive job.

correct. 

> It doesn't seem to work that way to me at all.  In particular the window
> manager can become almost totally usless if there are even few jobs running
> in background ... and even if they have been "NPRIed" into oblivion.

.. a 'few' jobs ? There is a caveat in this kind of setup as long as you are 
low in CPU power and core memory. Each job still exists, as before, in 
memory, and , maybe, it gets swapped out once in a while. But still, there 
is some residual memory blocked with information needed to get the process 
back to life if nothing else is to be done. The memory left for the other 
jobs is not that much as if the were alone.  

> 
> I have a 4D/20 with 8 meg ram running 3.2

Unix takes at least about 4, and windowing will need a few more. So if you're 
running out of memory on a 8 megs machine, it starts swapping on its (slow) 
SCSI disk. Have a look at the osview and look for the length of the running 
queues. They could easily be too large for the PI. 
I have a Mac with 8 Megs RAM, and run Decnet, Ethertalk, Appletalk, TCP/IP, 
and TOPS. Then there is a Pagemaker, a Word, and Statview, besides Versaterm 
Pro and Telnet. Once in a while I had to face the fact that a MacII is just 
not made for such many jobs. Same applies to your PI (without wanting to 
compare a PI with my Mac in terms of functionality 8-( and spped :-) ... )
According to the tests we did with a 4D/20 we had about a year ago, 8 megs 
and 3 npri'd jobs are sufficient to make NEWS very slow. There is no 
chance to run  Workspace on it because it takes ages. You could run ruptime 
and check that the load is less than 3. If you're higher, forget the PI. 
Our 120 (yessir, still someboxes of this kind around!) heavily drops 
performance once the load is larger than 6 (and it has two processors).  
  
First aid would be to npri the newsmanager to a reasonably high value 
(see the corresponding include file for details on npri ranges). 

My serious advice is to get more memory and at least a 25. 

Reinhard 

(Disclaimer: I'm not working for SGI.)