Date: Mon, 01 Apr 1996 02:30:18 -0800 From: David Greenman <davidg@Root.COM> To: Kees Jan Koster <dutchman@spase.nl> Cc: freebsd-hackers@FreeBSD.ORG (FreeBSD hackers Mailing list) Subject: Re: HDD cpu usage (IDE vs. SCSI). Message-ID: <199604011030.CAA08362@Root.COM> In-Reply-To: Your message of "Mon, 01 Apr 1996 11:03:46 %2B0200." <199604010903.LAA07931@deimos.spase.nl>
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>I was told that cpu usage of SCSI disks was lower than that of IDE disks. > >However: > >LikeEver (amd486DX4-100, ncr pci scsi controller) >Seagate -------Sequential Output-------- ---Sequential Input-- --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- >Directory MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU >/usr 20 1299 81.1 1263 15.5 653 18.2 1778 94.9 1982 41.8 47.7 5.7 >/tmp (mfs) 20 689 33.7 285 3.4 274 4.5 397 17.5 503 5.7 27.0 3.3 > >Maxtor -------Sequential Output-------- ---Sequential Input-- --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- >Directory MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU >/var 20 750 41.9 740 8.5 405 9.7 764 34.7 770 8.8 32.0 3.9 >/tmp (mfs) 20 948 48.5 479 6.4 481 9.3 772 39.0 1228 19.3 39.0 4.7 >/msdos 20 28 4.5 74 3.3 43 1.9 111 7.7 111 3.6 9.6 10.9 > >phobos (pentium 90, on-board IDE controller) >Quantum -------Sequential Output-------- ---Sequential Input-- --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- >Directory MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU >/usr 40 1215 41.7 1818 18.8 811 11.5 1376 41.0 1990 16.0 39.9 3.9 > >How come the seagate uses twice as much cpu as the quantum? Because a Pentium-90 is much faster than a 486-100 for certain things and most of the %CPU is for total I/O overhead, not just the overhead in the device driver. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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