From: =?iso-8859-1?Q?Agust=EDn?= Herrera <aherrera@datafull.com>
To: linux-kernel@vger.kernel.org
Cc: dgilbert@interlog.com
Subject: Re: Problems with scsi emulation
References: <3EDAD8AA.50503@interlog.com>
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Date: Tue, 13 Jan 1970 03:22:13 -0300
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> > I'm using a customized 2.4.20 kernel (red hat 9) with
> > scsi emulation, scsi  cdrom & scsi generic support
> > options enabled in .config and hdx-ide-scsi in
> > lilo.conf. apps as cdrecord or cdrdao take up all my
> > cpu time (I have a duron 1.1 gz, kt133, 192mb sdram,
> > 30 gb 5400 rpm hd). in windows (with dma enabled) Nero d
> > oesn't take up any (or almost) cpu time...
> > is this an issue of the linux-kernel or a configuration
> > problem?
> 
> Due to many problems with DMA locking up on ATAPI writers
> earlier in the lk 2.4 series, Linux takes a very
> conservative approach and turns off DMA.
> It can be turned back on with:
>  # hdparm -d 1 /dev/hdb
> assuming your cdwriter is found at /dev/hdb (even
> though the ide-scsi driver "owns" that device
> and you address it as /dev/scd0 ). You can get
> faster DMA modes with the addition of the "-X"
> switch in hdparm but that should not be necessary.
> 
Doug:

I've tried that, but it doesn't make any difference.

I've been able to do ficticious tweaks on /dev/hdc and hdd like, for 
example, activating dma mode 5 -which is virually impossible for a 
cdrom drive. Actually, as I'd disabled ide/atapi-cdrom support in the 
kernel I guess that /dev/hdc & hdd point to 'nowhere'. Anyway, with 
hdparm optimizations or without them processor time consumption remains 
at a 70 - 90 % so, clearly, I haven't made any progress.

The only interface for cdrom drives that i've enabled in the kernel is 
scsi (to be able to record and rip w/ cdrdao). I guess that the 
inability to use dma is related to that because my ide hard disks seem 
to be using it w/o problems (and obviously I'm not using scsi with 
them). Nevertheless, I can't set up a multcount higher than 8, which is 
really surprising because the ide chipset and the drives are quite new.

So I repeat my enquiry, Is all this a question configuration or of a 
kernel upgrade? I've already tried the latter, but, as far as I could 
appreciate, the current nvidia 'accelerated' drivers (1.0-4363) for my 
geforce2 didn't work with the 2.5 kernel (more precisely 2.5.69) I'd 
compiled. Once more, is this incompatibility a current issue of these 
kernels? In case it were an configuration error I would certainly do 
the upgrade because 2.5 kernel series seem to have many advantages, as 
for example, the inclusion of the alsa sound drivers.

Agust?n Herrera

PD: I've changed my adress to aherrera@datafull.com
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