From owner-freebsd-current Mon Nov 13 23:38:15 1995 Return-Path: owner-current Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id XAA05490 for current-outgoing; Mon, 13 Nov 1995 23:38:15 -0800 Received: from Root.COM (implode.Root.COM [198.145.90.17]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id XAA05485 for ; Mon, 13 Nov 1995 23:38:12 -0800 Received: from corbin.Root.COM (corbin [198.145.90.50]) by Root.COM (8.6.12/8.6.5) with ESMTP id XAA27972; Mon, 13 Nov 1995 23:38:11 -0800 Received: from localhost (localhost [127.0.0.1]) by corbin.Root.COM (8.6.12/8.6.5) with SMTP id XAA00133; Mon, 13 Nov 1995 23:38:10 -0800 Message-Id: <199511140738.XAA00133@corbin.Root.COM> To: Julian Elischer cc: uhclem%nemesis@fw.ast.com, simonm@dcs.gla.ac.uk, current@freebsd.org Subject: Re: Disk I/O that binds In-reply-to: Your message of "Mon, 13 Nov 95 23:25:12 PST." <199511140725.XAA26807@ref.tfs.com> From: David Greenman Reply-To: davidg@Root.COM Date: Mon, 13 Nov 1995 23:38:10 -0800 Sender: owner-current@freebsd.org Precedence: bulk >Actually here's an answer that might tackle it from another point.. >if the raised priority that a process get's after getting a block >is lower that the raised priority that a process gets after being suspended > for a second or two, then >in a busy system, whenever processes start getting held up the hog process >will start to lose out a little more.. and maybe if it get's its read of the >read-ahead buffer in just a little later, the head might have got a chance to >get past it in which case it will have to go all the way around again.. >at least in this method, an un busy system has less degradation.. > > >processes that read a lot are constantly cycling >into high priority after every read, but the sleeps are so short that >these processes are basically permanently at raised priority.. >especially with read-ahead and track caches making the disks so dammed fast Yes, this was the theory behind Matt Dillon's patches if my memory is correct (it might very well not be :-)). I think the problem is a composite of a variety of things. -DG