From owner-freebsd-current Fri Apr 7 06:12:43 1995 Return-Path: current-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id GAA05866 for current-outgoing; Fri, 7 Apr 1995 06:12:43 -0700 Received: from aries.ibms.sinica.edu.tw ([140.109.40.248]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id GAA05853 for ; Fri, 7 Apr 1995 06:12:20 -0700 Received: (from taob@localhost) by aries.ibms.sinica.edu.tw (8.6.11/8.6.9) id UAA20480; Fri, 7 Apr 1995 20:51:33 +0800 Date: Fri, 7 Apr 1995 20:51:32 +0800 (CST) From: Brian Tao To: FREEBSD-CURRENT-L Subject: Re: Label/slices : how to add a disk ? In-Reply-To: <199504070923.CAA07043@gndrsh.aac.dev.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: current-owner@FreeBSD.org Precedence: bulk On Fri, 7 Apr 1995, Rodney W. Grimes wrote: > > This is on a 16MB machine, P54C-90, NCR810 controller iozone 2.01: The > buffer cache become ineffective at 8MB transfer size, but still skewed > the numbers some (~200K/sec). [...] > Writing the 128 Megabyte file, 'iozone.tmp'...53.343750 seconds > Reading the file...51.906250 seconds > > IOZONE performance measurements: > 2516090 bytes/second for writing the file > 2585772 bytes/second for reading the file How much CPU is being eaten on your machine while performing the benchmark? My machine is a PCI 486DX4/100 machine (16 megs) with the NCR53810 controller and a Quantum Empire 1080. iozone 2.01: IOZONE writes a 128 Megabyte sequential file consisting of 16384 records which are each 8192 bytes in length. It then reads the file. It prints the bytes-per-second rate at which the computer can read and write files. Writing the 128 Megabyte file, 'iozone.tmp'...44.750000 seconds Reading the file...43.953125 seconds IOZONE performance measurements: 2999278 bytes/second for writing the file 3053656 bytes/second for reading the file 'top' shows this (sometime during the latter half of the run): PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND 20444 root 48 0 244K 424K run 0:41 51.76% 50.35% iozone Is this a reasonable figure? At 3000000 bytes/sec using 8192-byte blocks, the CPU is shuttling about 366 I/O operations a second or about 2.7 ms per operation. That sounds like "a lot of time" from a CPU's viewpoint, most of it spent waiting for the disk (I assume?). BTW, out of curiosity, if I do something like this: % time dd if=/dev/zero of=/dev/null bs=102400 count=10240 10240+0 records in 10240+0 records out 1048576000 bytes transferred in 30 secs (34952533 bytes/sec) 0.171u 28.688s 0:29.33 98.3% 56+529k 0+1io 0pf+0w ... just what am I measuring? CPU-to-RAM bandwidth? CPU-to-cache speed? Or nothing at all useful? :) -- Brian ("Though this be madness, yet there is method in't") Tao taob@gate.sinica.edu.tw <-- work ........ play --> taob@io.org