Bad SATA (Sil 3112A) performance with kernel 2.6.8

[Andrey Andreev]

Hi,

I upgraded my 2.6.6 kernel to 2.6.8 (the fedora update). I run a SATA 
drive on a Sil 3112A controller. I quickly noticed that the SATA drive 
was no longer visible under /dev/hde, but under /dev/sda, fixed my 
fstab, etc.

However, as Sil 3112 has had very varied performance with different 
kernels, and there obviously was a change in the way it worked, I ran:

[andrei at brie andrei]$ sudo /sbin/hdparm -t -T /dev/sda
/dev/sda:
  Timing buffer-cache reads:   1564 MB in  2.00 seconds = 780.95 MB/sec
  Timing buffered disk reads:   44 MB in  3.12 seconds =  14.11 MB/sec

Which is pretty awfuly slow, compared to 2.6.6 (over 50 MB/sec). 
Otherwise, I can spot no other errors or problems with it.

Any pointers as to what I should change? Is this a common result with 
that controller?

See the relevant dmesg part

8<--------------------------------------->8

SCSI subsystem initialized
libata version 1.02 loaded.
sata_sil version 0.54
ACPI: PCI interrupt 0000:01:0c.0[A] -> GSI 11 (level, low) -> IRQ 11
ata1: SATA max UDMA/100 cmd 0x2285D080 ctl 0x2285D08A bmdma 0x2285D000 
irq 11
ata2: SATA max UDMA/100 cmd 0x2285D0C0 ctl 0x2285D0CA bmdma 0x2285D008 
irq 11
ata1: dev 0 cfg 49:2f00 82:346b 83:7d01 84:4003 85:3469 86:3c01 87:4003 
88:207f
ata1: dev 0 ATA, max UDMA/133, 312581808 sectors: lba48
ata1(0): applying Seagate errata fix
ata1: dev 0 configured for UDMA/100
scsi0 : sata_sil
ata2: no device found (phy stat 00000000)
scsi1 : sata_sil
   Vendor: ATA       Model: ST3160023AS       Rev: 3.18
   Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB)
SCSI device sda: drive cache: write back
  sda: sda1 sda2
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0

8<--------------------------------------->8


TIA,

//Andro