Re: kernel performance problem

[Walt H]

> This is my first ever posting  to this list, so please excuse me if I've 
> f**cked up and broken protocol.
> I use an IDE LG DVD-RW drive for backup(GSA-4081B).
> Back around 2.6.10 it wrote at typically 1.6-1.7x speed, but thereafter  
> it dropped to  around 0.6-0.7 x.
>
>
> %hdparm -I /dev/hdd
>
> /dev/hdd:
>
> ATAPI CD-ROM, with removable media
>        Model Number:       HL-DT-ST DVDRAM GSA-4081B              
>        Serial Number:      K2B3CFE4600        
>        Firmware Revision:  A100   
> Standards:
>        Likely used CD-ROM ATAPI-1
> Configuration:
>        DRQ response: 50us.
>        Packet size: 12 bytes
> Capabilities:
>        LBA, IORDY(can be disabled)
>        DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2
>             Cycle time: min=120ns recommended=120ns
>        PIO: pio0 pio1 pio2 pio3 pio4
>             Cycle time: no flow control=120ns  IORDY flow control=120ns
> HW reset results:
>        CBLID- below Vih
>        Device num = 1

Hi Andrew,

I know that hdparm shows udma2 mode selected for data transfers, but 
check that dma is *actually* turned on.  ie:  hdparm -d1 /dev/hdd

I don't remember exactly when this went in, but there were some IDE 
patches around the 2.6.11 or so timeframe that seemed to change the way 
these devices get setup at boot.  I believe this happened when the 
autotune= syntax was deprecated.  HTH,

-Walt



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