Extreme IDE slowdown with 2.2.18

[Robert Högberg <robho956@student.liu.se>]

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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