From owner-freebsd-current Sat Sep 6 14:40:22 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id OAA04260 for current-outgoing; Sat, 6 Sep 1997 14:40:22 -0700 (PDT) Received: from sos.freebsd.dk (sos.freebsd.dk [195.8.129.33]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id OAA04254 for ; Sat, 6 Sep 1997 14:40:18 -0700 (PDT) Received: (from sos@localhost) by sos.freebsd.dk (8.8.7/8.7.3) id XAA07333; Sat, 6 Sep 1997 23:40:25 +0200 (MEST) From: Søren Schmidt Message-Id: <199709062140.XAA07333@sos.freebsd.dk> Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) In-Reply-To: <199709061909.VAA25891@kairos> from Mats Lofkvist at "Sep 6, 97 09:09:41 pm" To: mal@algonet.se (Mats Lofkvist) Date: Sat, 6 Sep 1997 23:40:24 +0200 (MEST) Cc: current@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL30 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-freebsd-current@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk In reply to Mats Lofkvist who wrote: > For fun I tested the dd benchmark on my new machine (intel providence > board with pp200, 64M, quantum viking 4.5G uw connected to the aic7880). > > As long as I run the dd with the machine idle, I get over 10MB/s. > But with a single cpu-bound process running, the throughput drops > to less than 1.5MB/s with 64k blocks (and it gets even worse with > smaller blocks). Hmm juist tried this on current with EIDE disk and DMA turned on: Machine is a P6@233/64M/Maxtor EIDE/current as of just now... Nice -19 loop (being a tight CPU loop). # dd if=/dev/rwd0 of=/dev/null count=800 bs=64k 800+0 records in 800+0 records out 52428800 bytes transferred in 10.904597 secs (4807954 bytes/sec) This is about half the rate as on an unloaded system... So maybe this is handled better in current, or EIDE w/DMA is not as bad as people think. The only advantage with SCSI these days seems to be the ability to add more than 4 devices easily, and to add them externally of the machine. But then again you have to pay solid bucks to get that :) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Søren Schmidt (sos@FreeBSD.org) FreeBSD Core Team Even more code to hack -- will it ever end ..