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From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
Message-Id: <199604301634.JAA13493@GndRsh.aac.dev.com>
Subject: Re: lmbench IDE anomaly
To: koshy@india.hp.com (A JOSEPH KOSHY)
Date: Tue, 30 Apr 1996 09:34:21 -0700 (PDT)
Cc: hackers@freebsd.org, current@freebsd.org
In-Reply-To: <199604301053.AA141971583@fakir.india.hp.com> from A JOSEPH KOSHY at "Apr 30, 96 04:23:03 pm"
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> 
> Running lmdd on a -current system supped around mid apr:
> 
> ----
> >> single lmdd run on scsi disk
> 
> krill# lmdd if=/dev/rsd0a of=internal bs=1024 count=8192 #  SCSI disk, aha1542
> 8.00 MB in 11.35 secs, 721.92 KB/sec
> 
...
> However when the same exercise is repeated with the IDE disk:
> 
> ----
> krill# lmdd if=/dev/rwd0a of=internal bs=1024 count=8192 #  IDE disk
> 8.00 MB in 9.17 secs, 892.89 KB/sec
...
> 
> Here we see a 8x degradation per process; 4x in terms of total throughput.
> 
> Is this to be expected, or am i doing something wrong here? The system was 
> otherwise idle during these tests.

run those command with a ``time'' in front of them as in:
time lmdd if=/dev/rwd0a of=internal bs=1024 count=8192 #  IDE disk

You may be seeing CPU saturation effecting the ability of the system to
keep the disk drive busy due to the fact that the wd class disks have to
do rep insb to copy the data from the disk to memory where as the 1542
does this with bus mastering.

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD