Unable to enable DMA on some AMD systems

Christoph Wiesen chris at deadhand.com
Mon Jun 6 16:09:37 CDT 2005


Am Sonntag 05 Juni 2005 20:31 schrieb Thomas Hofer:
> Looking at /etc/init.d/hdparm, I'd say that /etc/hdparm.conf is the
> right place to configure the hdparm defaults for the drives, if
> necessary.
>
> bye,
> Thomas.

Ok, /etc/hdparm.conf was the correct place to go. I now have working DMA 
enabled at bootime for both my DVD drives.

Unfortunately system performance is bad right now - really bad. The sentence I 
just wrote appeared on screen only after a few seconds.
This is while I'm copying some files from ~ to /data - both are partitions on 
the same SATA harddisk. Hmm, burning DVDs worked fine now by the way.

Anyway i'll have to see if again removing the via module from /etc/modules 
(thus loosing dma for the dvd-drives) will fix this issue again - at least I 
think it wasn't so bad before, when I  copied files. Now transfer rates drop 
below 1MB/s and then stay around 1.2MB/s which really isn't what a SATA drive 
should do.

But to me 'hdparm -tT /dev/sda' seems to be ok:

/dev/sda:
 Timing cached reads:   2268 MB in  2.00 seconds = 1133.04 MB/sec
 Timing buffered disk reads:  158 MB in  3.01 seconds =  52.41 MB/sec

This is with the exact settings I'm using now. But starting a copy with 
Konqueror (kio_file) will first make it 'crawl' at 1.2MB/s and then, when I 
dare to do something like open a text file in kate make my whole system so 
slow it's not useable anymore and I have to stop the copy to regain control. 

But what to 'blame' I do not know - and I seem to be run out of options. At 
least i do not know what else to do now. So basically I'm lost again.

Tomorrow I'll see how it behaves without first loading the via module (so 
without using dma on the ide devices). It's too late today. I just wanted to 
write this to the list first, hoping someone can help me here again.

Kind regards,

Chris



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