poor performance on big machine

[Simon 'corecode' Schubert]

hey,

I just continued building and noticed that we seem to have a horribe hdd performance:

Disks   ad4   ad6  acd0   cd0 pass0   md0
KB/t   0.00 44.27  0.00  0.00  0.00  0.00
tps       0   186     0     0     0     0
MB/s   0.00  8.03  0.00  0.00  0.00  0.00 
% busy    0   100     0     0     0     0  
            ^^^^^
             100%?

A lot of processes are in states getblk, wdrain, biowr, biord.  Not stuck, but real slow.  Everybody is pounding on ad6.

atapci0: <Intel ICH5 UDMA100 controller> port 0xfc00-0xfc0f,0x376,0x170-0x177,0x3f6,0x1f0-0x1f7 irq 6 at device 31.1 on pci0
ata0: <ATA channel 0> on atapci0
acd0: DVDROM <HL-DT-ST DVD-ROM GDR-8084N/1.01> at ata0-master UDMA33
ata1: <ATA channel 1> on atapci0
atapci1: <Intel ICH5 SATA150 controller> port 0xcc80-0xcc8f,0xcc98-0xcc9b,0xcca0-0xcca7,0xccb0-0xccb3,0xccb8-0xccbf irq 6 at device 31.2 on pci0
ata2: <ATA channel 0> on atapci1
ad4: 152587MB <Maxtor 6L160M0 BACE1G10> at ata2-master SATA150
ata3: <ATA channel 1> on atapci1
ad6: 152587MB <WDC WD1600JS-75NCB2 10.02E03> at ata3-master SATA150
IRQ stats are:
1140 total
435 clk
 26 uhci0
435 atapci1
 26 em0
    ata0
    irq19
218 irq21
For some reason "test" was also several times in "biowr".  First, I don't understand why test is used and not the builtin, but whatever.  What's the business of test reading something?  Might that be urandom and stackprotector?  When else would test read a block?

cheers
 simon