[6210] in linux-scsi channel archive
Re: Probably a silly problem ..
daemon@ATHENA.MIT.EDU (Dietmar Stein)
Mon Mar 29 23:35:35 1999
Date: Tue, 30 Mar 1999 06:22:21 +0200
To: Monty <xiphmont@mit.edu>, linux-scsi@vger.rutgers.edu
From: dstein2203@t-online.de (Dietmar Stein)
I didn't know much about the memory management of kernel 2.2 - but it was the
only idea I had.
Dietmar
Monty wrote:
> >> Warning: Running low on SCSI DMA buffersWarning: Running low on SCSI DMA
> >> buffersWarning: Running low on SCSI DMA buffers
> >> etc etc, hundreds of times over.
> >
> >Hm, it seems that the buffer is running low which might end in a write-error
> >(buffer underrun)... You are using the aha154x; I think there is an option in
> >the BIOS of the controller to choose the DMA-channel... (on 1542 there is).
> >Make sure that the channel (I think default is DMA 6) is not in use by
> >another device which has direct memory access (soundcard and so on).
>
> I believe this has nothing to do with the DMA channel. If I recall
> Doug Gilbert's DMA/memory rants properly, ISA SCSI cards have to do
> DMA under the 16MB level, and Linux 2.2 memory management is so
> aggressive about managing higher memory, that it leaves almost no
> space under 16M for ISA DMA. His quote is "the more RAM you have, the
> less space you have under 16M" or something exactly to that effect.
>
> Downgrade to 2.0, invest in a PCI SCSI adapter, or convince the VM
> tuning folks that they did a Bad Thing (tm)....
>
> Monty
>
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