From owner-freebsd-hackers Tue Sep 10 03:24:52 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id DAA07162 for hackers-outgoing; Tue, 10 Sep 1996 03:24:52 -0700 (PDT) Received: from who.cdrom.com (who.cdrom.com [204.216.27.3]) by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id DAA07155 for ; Tue, 10 Sep 1996 03:24:48 -0700 (PDT) Received: from root.com (implode.root.com [198.145.90.17]) by who.cdrom.com (8.7.5/8.6.11) with ESMTP id DAA06462 for ; Tue, 10 Sep 1996 03:24:47 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by root.com (8.7.5/8.6.5) with SMTP id DAA17937; Tue, 10 Sep 1996 03:22:57 -0700 (PDT) Message-Id: <199609101022.DAA17937@root.com> X-Authentication-Warning: implode.root.com: Host localhost [127.0.0.1] didn't use HELO protocol To: Michael Smith cc: lars@elbe.desy.de (Lars Gerhard Kuehl), Duncan.Barclay@pa-consulting.com, hackers@FreeBSD.org Subject: Re: undocumented kernel priority changing In-reply-to: Your message of "Tue, 10 Sep 1996 19:22:28 +0930." <199609100952.TAA05559@genesis.atrad.adelaide.edu.au> From: David Greenman Reply-To: dg@root.com Date: Tue, 10 Sep 1996 03:22:57 -0700 Sender: owner-hackers@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk >Lars Gerhard Kuehl stands accused of saying: >> >> For sites with only a few active processes that isn't a problem at all. >> (No competition.) If there are many active processes 'renicing' is highly >> desirable. The limit is usually reached only by jobs submitted >> with 'interactive' nice levels. It might be an advantage to increase >> the limit if someone likes to use xemacs on a 16MHz 386SX. >> (10 minutes cpu time even on a 100 MHz 586 is pretty a lot ;) > >It's peanuts for long-lived processes in any sort of 'embedded' application: > >mstradar:/home/radar>uptime >11:49AM up 23:35, 3 users, load averages: 0.19, 0.27, 0.25 >mstradar:/home/radar>ps ax >... > 8651 ?? SN 36:01.06 /home/radar/rd12/libexec/FreeBSD/exptd -f /home/radar > 3303 p0- SN 83:44.55 /usr/local/rsi/idl//bin/bin.linux/idl analysis_init > >As you can see, it's been up less than a day, and the current load is pretty >low. Depending on configuration, with just these two running the system >will push a load average of 1.8 or more nonstop. (These two also normally >start out of /etc/rc.local, so they've been restarted some time after >the system booted.) > >Your point about only having a few processes is quite valid though - there's >no problem with either responsiveness or overall performance there. FreeBSD already has a sophisticated mechanism for controlling process priorities (not nice value) for CPU hungry processes. The code in mi_switch() looks like a total hack to me and should be removed in my opinion. Nothing except the user or superuser should change the 'base scheduling priority' ("nice" value) of a process - certainly not automagically in the kernel. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project