Apur-ee.207 net.unix-wizards utcsrgv!utzoo!decvax!pur-ee!bruner Tue Jan 19 11:30:06 1982 crunchers and 'nice' On the Purdue (Engineering) network machines, we added another p_flag which is known as the "research bit". This bit is set in clock() when a process accumulates more than "tschd" seconds of CPU time. Processes with a "nice" less than PZERO are immune to this action. (There are also provisions to turn it off if the job does a lot of terminal waiting.) This bit increases (degrades) the running priority of a job, and also invokes some disfavored swapping algorithms. For instance, one change (very helpful on 11/45's) prevents runnable "research" jobs for which there is no main memory available (i.e. can't be swapped in without something else going out) from coming in for "swait" seconds. Non-"research" jobs are not subject to this provision. This cuts down swapping (a critical factor on small machines). The combination of the degraded priority and disfavored swapping on the crunchers gives short, interactive programs good response time. "tschd" and "swait" can be patched with a debugger to allow some operator adjustment when the load is high. We also have a "nicer" facility, and a "forced rollout" at 127 (V6) 39 (V7). We implemented "nicer" as a system call with the same semantics as "kill" (0 gets all processes in the process group, etc.) In addition, any user is permitted to use "nicer" to increase p_nice for his own processes. --John Bruner ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.