From owner-freebsd-current Sat Sep 16 12:32:31 2000 Delivered-To: freebsd-current@freebsd.org Received: from gidora.zeta.org.au (gidora.zeta.org.au [203.26.10.25]) by hub.freebsd.org (Postfix) with SMTP id 424B637B422 for ; Sat, 16 Sep 2000 12:32:26 -0700 (PDT) Received: (qmail 12996 invoked from network); 16 Sep 2000 19:32:22 -0000 Received: from unknown (HELO bde.zeta.org.au) (203.2.228.102) by gidora.zeta.org.au with SMTP; 16 Sep 2000 19:32:22 -0000 Date: Sun, 17 Sep 2000 06:32:19 +1100 (EST) From: Bruce Evans X-Sender: bde@besplex.bde.org To: Alexander Leidinger Cc: current@FreeBSD.ORG, jhb@FreeBSD.ORG Subject: Re: 100% system time? (SMPng on UP system) In-Reply-To: <200009161501.e8GF13n01686@Magelan.Leidinger.net> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Sat, 16 Sep 2000, Alexander Leidinger wrote: > dnetc runns with idprio 31, system cvsupped around Sep 16, 11 CEST from > a german mirror (it contains the idle fixes: src/sys/kern/kern_idle.c,v > 1.4), complete build{world,kernel}. > > ---snip--- > last pid: 1666; load averages: 1.10, 1.11, 1.03 up 0+00:51:21 16:54:14 Perhaps it really is a system process :-[. idprio on a pure cpu hog prevents other user processes from running like a system process might do: idprio 31 sh -c "while :; do :; done" System processes actually hang the entire system until they complete: dd if=/dev/random of=/dev/null bs=10m count=1 This takes 32 seconds on a Celeron 366 overclocked to 523, during which time no other processes, including interrupt tasks, can run. This is because the supergiant lock prevents context switching while the i/o is being done. There is nothing special about /dev/random here except that it has a low transfer rate. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message