Extreme IDE slowdown with 2.2.18

Hello,

I'm having problems with the performance of my harddrives after I upgraded my kernel from 2.2.17 to 2.2.18.
The performancedrop is noticable on every IDE drive.

Here are some numbers to show what I mean:

2.2.17:
/dev/hdc:
Timing buffered disk reads: 64 MB in 4.32 seconds =14.81 MB/sec

2.2.18:
/dev/hdc:
Timing buffered disk reads: 64 MB in 10.49 seconds = 6.10 MB/sec

These are hdparm -t outputs and the performance drop is pretty noticable :-/

I also copied a 600Mb file from my HDD to /dev/null and the results were:

2.2.17: 1 minute 9 seconds
2.2.18: 1 minute 38 seconds

My system consists of:
FIC VA-503+ motherboard with the MVP3 chipset
K6-2 500MHz
128Mb SDRAM
3 IDE disks (see below)
Slackware 7.0

dmesg output for the IDE system (no differences between .17 and .18):

VP_IDE: IDE controller on PCI bus 00 dev 39
VP_IDE: not 100% native mode: will probe irqs later

    ide0: BM-DMA at 0xe400-0xe407, BIOS settings: hda:DMA, hdb:DMA
    ide1: BM-DMA at 0xe408-0xe40f, BIOS settings: hdc:DMA, hdd:DMA

hda: QUANTUM FIREBALL ST6.4A, ATA DISK drive
hdb: QUANTUM FIREBALL SE4.3A, ATA DISK drive
hdc: IBM-DJNA-352030, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
hda: QUANTUM FIREBALL ST6.4A, 6149MB w/81kB Cache, CHS=784/255/63
hdb: QUANTUM FIREBALL SE4.3A, 4110MB w/80kB Cache, CHS=524/255/63
hdc: IBM-DJNA-352030, 19470MB w/1966kB Cache, CHS=39560/16/63

When I performed the tests I used similiar .17 and .18 kernels with a minimum components included. No network, SCSI, sound and such things. .config files can be supplied if needed.

Does anyone know what could be wrong? Have I forgot something? Is this a known problem with the 2.2.18 kernel?

Thanks in advance!

Robert

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[snip]

Is DMA enabled on the hard drives?
Did you turn on "Use DMA by default" in the kernel configuration? Did you compile in DMA support (if needed)?

What is the output of "hdparm /dev/hda /dev/hdb /dev/hdc" ?

Rob Adamson.

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