job00542@uxa.cso.uiuc.edu (06/27/90)
I am working on a parallel Fortran program for the Sequent Balance and am having difficulties getting accurate timings because the results vary with the system load, even though I'm measuring CPU time. I've heard that gang scheduling of processes will help-- does anyone know how to do this? Thanks in advance... James Bordner
hafner@ordin.cs.wisc.edu (Brian J. Hafner) (06/28/90)
In article <63900005@uxa.cso.uiuc.edu> job00542@uxa.cso.uiuc.edu writes: > >I am working on a parallel Fortran program for the Sequent Balance and am >having difficulties getting accurate timings because the results vary with the >system load, even though I'm measuring CPU time. I've heard that gang >scheduling of processes will help-- does anyone know how to do this? Thanks in advance... > >James Bordner Gang scheduling is a way to utilize a group of processors without any interference from the OS. Essentially, the processors are removed from the "pool" of free processors and completely assigned to the user. I knew that the Encore Multimax could do this, but wasn't aware that the Sequent [Balance | Symmetry] could. Sequent offers two privledged system calls: proc_ctl() which allows a user to fix the priority of a process and prevent aging. tmp_affinity() which glues a process to a particular processor. Although the OS still is charge of all the processors, these calls can be used to fake gang scheduling. Brian J. Hafner Computer Sciences Department University of Wisconsin - Madison hafner@cs.wisc.edu
job00542@uxa.cso.uiuc.edu (06/28/90)
/* Written 10:21 pm Jun 27, 1990 by hafner@ordin.cs.wisc.edu in uxa.cso.uiuc.edu:comp.sys.sequent */ > Gang scheduling is a way to utilize a group of processors without > any interference from the OS. Essentially, the processors are removed > from the "pool" of free processors and completely assigned to the > user. Thanks! Luckily, I found a gang scheduler for the Balance-- written by Dr. Eugene Brooks and available via anonymous ftp to maddog.llnl.gov. I haven't tried it yet, but it looks promising. James Bordner