Re: [Demo program]: Poor elevator performance in 2.4.0-test9pre6

From: Matthew Fredrickson (lists@frednet.dyndns.org)
Date: Wed Sep 27 2000 - 16:47:56 EST


On Wed, Sep 27, 2000 at 04:10:38PM +1000, Robert Cohen wrote:
>
> lists@frednet.dyndns.org wrote
>
> I doubt this has any relevance whatsoever, but when I try this on a
> 2.2.16
> kernel running on top of a Pentium Pro 200 w/96megs of mem w/ a SCSI 2
> disk, I get some funny numbers:
>
> matt@zeus:~/cwork/personal$ ./elv_test 8 30
> files created, 240 megs written at 4.32 megs/sec
> finished writing 240 megs written at 1794.23 megs per sec
> finished reading, 240 megs read at 1675.813817 megs/sec
>
> Any ideas why I would be getting these numbers?
> -
>
> That will teach me to play fast and loose with checking error returns
> from system calls. I wasnt specifying a mode when creating the files.
> So they were being created without user write permission..
> I dont know why it worked under 2.4.0. Maybe a kernel bug :-).
>
> Anyway, a new version is available now at
> http://tltsu.anu.edu.au/~robert/elv_test.c

Ah, thanks. I have much more likely results now:
matt@zeus:~/cwork/personal$ ./elv_test2 8 30
files created, 240 megs written at 3.91 megs/sec
finished writing 240 megs written at 2.28 megs per sec
finished reading, 240 megs read at 0.909702 megs/sec

BTW, why would the first incorrectly function in kernel 2.2? A bug
<cough>feature</cough>?
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