From: Axel Farr Newsgroups: comp.parallel.pvm Subject: Re: pvm on multiprocessor smp linux and sgi machines Date: Thu, 22 Jul 1999 11:21:45 +0200 Organization: Technische Universitaet Darmstadt Message-Id: <3796E2A9.678E4EBE@physik.tu-darmstadt.de> References: <3794EA7F.D0B26813@designlab.ukans.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Xref: ukc comp.parallel.pvm:8595 Matthew Copeland wrote: > > I have recently been playing around with pvm3.4.1 on two Dual PII-333, > and an SGI Origin 2000 (6 processors). I have managed to get the > Pentium-IIs talking to each other, but I when I fire off a job, it only > uses one of the processors on each machine, rather than both of the > processors on each machine. > A similar problem occurs when I am attempting to fire off a job for the > origin. It will use one processor, but not more than that. What do I > need to do to get pvm to recognize the fact that their are multiple > processors in the machine and to make use of them. > > Matthew PVM processes are single-threaded. So you must start at least one job for each processor. On my Dual-PII Machine, I use 2 or 4 processes. The advantage of 4 processes over 2 is the fact, that a switch between two processors should not occur as often as in the case with 2 processes, because when a job has it current ammount of processing time eaten up, there is still one job waiting which ran on the same processor before, so that one will be choosen instead of one of the other jobs which where running on the other CPU. With one two working processes, it could happen, that one process is waiting for cpu, because it CPU does some other work, the other process has eaten up its CPU time, and if the waiting process ist the only process in the ready-queu, it will then continue on the other CPU causing some overhead, because 512 kByte of cached memory will have to be moved from one CPU to the other. Axel Farr