[9fans] Enabling DMA causes newlines on console

[9fans] Enabling DMA causes newlines on console

[zfolkerts]

Hi,

If I enable DMA on my disks I get blank lines on the console whenever
I do disk I/O. Basically this prevents me from using rio while any
I/O is happening. I think there may be a blank message echoed to the
console in the IDE driver or somewhere. This does not happen if I do
not have DMA enabled. This seems to happen even if I only enable DMA on
one disk. It also seems to happen on both the onboard and offboard
controllers. I have not yet done extensive testing(I set up this server
yesterday), so I am unsure if this happens only with reads, writes or
both.

My setup is as follows:
The onboard IDE is a VIA, it is one of the VT82C69xx chipsets.
	(I am not at the machine now, and I don't remember the exact #)
The offboard IDE is a Promise Ultra 100.

My disk layout looks like this:
	/dev/sdC0/fs      1Gb kfs (What I am currently booting from)
	/dev/sdC0/fossil  20Gb fossil
	/dev/fs/isect0    1Gb index
		/dev/sdE0/isect0
		/dev/sdF0/isect0
	/dev/fs/arenas0   17Gb arena
		/dev/sdE0/arenas0
		/dev/sdF0/arenas0

So if I do this:
# for (i in sdC0 sdE0 sdF0)
	echo 'dma on' > /dev/^$i^/ctl
# con -l /srv/fscons
prompt:
main: snap -a

A couple of seconds later, when the data is sent off to venti, I will get
blank lines scroll through the center of my display, as if a message were
being printed on the console, but no text appears. Any ideas as to the
cause/prevention of this behavior? I never had DMA enabled on the
previous fossil/venti fileserver that I had, so I have only seen this
happen on this box. None of my other machines running Plan 9 have disks
in them, so I have only seen this happen on this machine.

Thanks,
Zack Folkerts

Re: [9fans] Enabling DMA causes newlines on console

[andrey mirtchovski]

On Mon, 14 Jul 2003 zfolkerts@starcenter.tn.org wrote:

> If I enable DMA on my disks I get blank lines on the console whenever
> I do disk I/O. Basically this prevents me from using rio while any
> I/O is happening. I think there may be a blank message echoed to the
> console in the IDE driver or somewhere. This does not happen if I do
> not have DMA enabled. This seems to happen even if I only enable DMA on

funny, this happens to me when I have DMA _disabled_...

Re: [9fans] Enabling DMA causes newlines on console

[jmk]

On Mon, 14 Jul 2003 zfolkerts@starcenter.tn.org wrote:
> If I enable DMA on my disks I get blank lines on the console whenever
> I do disk I/O. Basically this prevents me from using rio while any
> I/O is happening. I think there may be a blank message echoed to the
> console in the IDE driver or somewhere. This does not happen if I do
> not have DMA enabled. This seems to happen even if I only enable DMA on

do a simple test - bring the system up to a shell prompt (i.e. no window
manager) - enable dma then dd from one of discs to /dev/null, see what happens.
venti has a bad habit of writing to stdout/stderr.

Re: [9fans] Enabling DMA causes newlines on console

[zfolkerts]

On Mon, Jul 14, 2003 at 10:50:38AM -0400, jmk@plan9.bell-labs.com wrote:
> On Mon, 14 Jul 2003 zfolkerts@starcenter.tn.org wrote:
> > If I enable DMA on my disks I get blank lines on the console whenever
> > I do disk I/O. Basically this prevents me from using rio while any
> > I/O is happening. I think there may be a blank message echoed to the
> > console in the IDE driver or somewhere. This does not happen if I do
> > not have DMA enabled. This seems to happen even if I only enable DMA on
>
> do a simple test - bring the system up to a shell prompt (i.e. no window
> manager) - enable dma then dd from one of discs to /dev/null, see what happens.
Well, I rebooted the box, and found that there was no longer a partition
table on either of the drives attached to the Promise controller(lc
/dev/sd[EF]0 only gives ctl data and raw). Other than that, these were
the results:
	with dma on:
		/dev/sdC0	no newlines to console
		/dev/sd[EF]0	newlines to console
	with dma off:
		/dev/sdC0	newlines to console
		/dev/sd[EF]0	newlines to console

Could enabling dma on the Promise controller have trashed the partition
table? (I seem to remember a message to 9fans saying some controllers
trash data with dma enabled) Also which controllers are recommended? I
also have a Promise Ultra 66, and a CMD 640b(I haven't tried to use this
under Plan 9 since it is so old). Luckily I have my fossil on the first
drive in the system, so I don't have to recreate that, however I am
curious whether I should just get rid of the offboard controller entirly
making one of the drives slave to another. I had originally put the
Ultra 100 in so I could keep all of my disks as masters. Any suggestions
are appreciated.

Thanks,
Zack Folkerts

Re: [9fans] Enabling DMA causes newlines on console

[bs]

> Could enabling dma on the Promise controller have trashed the partition
> table?
 From what I have heard, the Promise controller is a very naughty one.
Even provisioning Windows via automated mechanisms are a problem.