Re: Abysmal PATA IDE performance

[Stephen Clark]

Tejun Heo wrote:

> Stephen Clark wrote:
> [--snip--]
>  
>
> > ata1: SATA max UDMA/133 cmd 0x1F0 ctl 0x3F6 bmdma 0xFFA0 irq 14
> > scsi0 : ata_piix
> > Synaptics Touchpad, model: 1, fw: 6.1, id: 0xa3a0b3, caps: 0xa04713/0x10008
> > input: SynPS/2 Synaptics TouchPad as /class/input/input1
> > ATA: abnormal status 0x7F on port 0x1F7
> > ata2: PATA max UDMA/100 cmd 0x170 ctl 0x376 bmdma 0xFFA8 irq 15
> > scsi1 : ata_piix
> > ata2.00: ATA-6, max UDMA/100, 117210240 sectors: LBA48
> > ata2.00: ata2: dev 0 multi count 16
> > usb 2-2: new low speed USB device using uhci_hcd and address 3
> > ata2.01: ATAPI, max UDMA/33
> > ata2.00: configured for UDMA/33 <==== why isn't this 66 or 100 ?
> >    
>
> See below.
>
>  
>
> > ===============****
> > usb 2-2: configuration #1 chosen from 1 choice
> > input: Logitech USB-PS/2 Trackball as /class/input/input2
> > input: USB HID v1.00 Mouse [Logitech USB-PS/2 Trackball] on
> > usb-0000:00:1d.1-2
> > ata2.01: configured for UDMA/33 <=========== is this related to the
> > following 2 lines? ====
> >    
>
> Nope,
>
>  
>
> >  Vendor: ATA       Model: HTS721060G9AT00   Rev: MC3O
> >  Type:   Direct-Access                      ANSI SCSI revision: 05
> > SCSI device sda: 117210240 512-byte hdwr sectors (60012 MB)
> > sda: Write Protect is off
> > sda: Mode Sense: 00 3a 00 00
> > SCSI device sda: drive cache: write back
> > SCSI device sda: 117210240 512-byte hdwr sectors (60012 MB)
> > sda: Write Protect is off
> > sda: Mode Sense: 00 3a 00 00
> > SCSI device sda: drive cache: write back
> > sda: sda1 sda2
> > sd 1:0:0:0: Attached scsi disk sda
> >    
>
> The above is for ata2.00.
>
>  
>
> >  Vendor: HL-DT-ST  Model: DVDRAM GMA-4082N  Rev: HJ02
> >  Type:   CD-ROM                             ANSI SCSI revision: 05
> >    
>
> And, this for ata2.01.
>
> PATA devices occupying the same channel literally share the cable, and 
> the driver needs to configure PIO mode of both devices to the slowest of 
> the two (PIO mode is always configured regardless of actual transfer 
> mode).  UDMA mode doesn't save such restriction, so devices can be 
> configured to its own maximum transfer mode.
>
> libata, until recently, simply used the slowest max transfer mode for 
> both PIO and UDMA modes (MWDMA too).  So, that's what's happening to 
> you.  Your cdrom's max UDMA mode is UDMA/33, so libata is using it for 
> both devices on the channel.  Recent kernels (2.6.19-rcX) don't have 
> this restriction.  Give 2.6.19-rc5 a shot.
>
>  
Hi Tejun,

Thanks for the info, I had started looking at the libata code but hadn't 
progressed very far.

Steve

--

"They that give up essential liberty to obtain temporary safety, 
deserve neither liberty nor safety."  (Ben Franklin)

"The course of history shows that as a government grows, liberty 
decreases."  (Thomas Jefferson)



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