[738] in linux-scsi channel archive
Re: Boot Kernels and performance options
daemon@ATHENA.MIT.EDU (Paul Gortmaker)
Wed Nov 1 09:04:03 1995
From: Paul Gortmaker <gpg109@rsphy1.anu.edu.au>
To: lnz@dandelion.com (Leonard N. Zubkoff)
Date: Wed, 1 Nov 1995 22:09:15 +1100 (EST)
Cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <199511010025.QAA07540@dandelion.com> from "Leonard N. Zubkoff" at Oct 31, 95 04:25:43 pm
>The issue I'm looking to address is the following. By default, my new BusLogic
>driver will have it's performance features enabled, such as tagged queuing and
>multiple outstanding commands per logical unit, but command line options will
>allow control over these features as necessary to compensate for buggy hardware
>or poorly configured SCSI systems. However, it would be nice to also give
>folks with buggy or poorly configured hardware the possibility of installing
>successfully. Once their system is installed, they can use kernel command line
>options to turn off tagged queuing if necessary, or to reduce the concurrency,
>but I don't see a way to do this during installation from boot floppy.
>
>Since a large number of users will never build custom kernels, I am unwilling
>to cripple the standard driver to support broken hardware, nor do I really
I don't think that having TQ disabled and no mult. outstanding commands
really qualifies as crippled. (If so, then all 1.2.x kernels are
crippled as shipped. ;-) Those people who don't build a custom kernel
are usually not the ones who try to squeeze out every last byte of i/o
bandwidth anyway.
This issue parallels that of IDE drives with broken firmware that claim
to support multiple sector transfers per interrupt (aka block mode) but
then fall over horribly if you try to use it. Because of that, block
mode is not enabled by default in the ide driver. Instead you have to
use a separate program (hdparm) to ioctl() the device and invoke the
performance options you desire.
I feel that a similar strategy can be used effectively for the buslogic
driver. Then everybody can install without extra magic required, and
they can later invoke the "speed" options without recompiling the kernel
as well. Everybody is happy.
Paul.
