Slow scsi performance under 1.3.77

yuri@poly21.rgti.com
Fri, 22 Mar 1996 15:38:46 -0500


Hello,

I'm having performance problems with the scsi subsystem under kernel
1.3.77. I have two drives: a Seagate ST32550N and Quantum XP34301 on a DPT
SmartCache III controller. Copying a 33mb file from one location to another
on the same disk takes about 27 seconds - pretty slow for 7200 RPM drives.
Here is where it gets even weirder. Copying a 33mb file from one drive to
another also takes about 27 seconds. Correct me if I'm wrong but shouldn't it
take about half the time? I've also tried running several disk benchmarks
(the Byte Unix bench and bonnie) - they all give rather low scores - about
half the throughput I've seen on the same drives under BSD. Running the
benchmarks in parallel on separate disks results in an ADDITIONAL 40-50%
reduction in throughput.

Here is my configuration: Micronics P5-133 Triton motherboard, 32MB EDO.
The DPT (IRQ 11) has scsi id 7, the Quantum is 6 and the Seagate is 2.
The scsi bus transfer speed is set to syncronous at 10mhz and is
terminated actively at the controller and passively at the Seagate. There is
also an ide cdrom hanging off IRQ 14, a 3com 3c509 at IRQ 10 and a Matrox
Millenium doing something or other with IRQ 9. The kernel is built without
the Triton chipset support. All disk partitions are formatted with ext2.

Recently i've tried substituting a Tekram DC-390 controller for the
DPT. Separate drives work ok - but when there is heavy disk activity on
both drives I get the following message repeated over and over for both
drive id's:

scsi : aborting command due to timeout : pid 6561, scsi0, channel 0, id 2, lun 0 Write (10) 00 00 2c 0a ec 00 00 16 00
--------------------------------------------------------------------------
scsi0 : AM53C974_abort called -- trouble starts!!
AM53C974 register dump:
IO base: 0xfc00; CTCREG: 0x0000; CMDREG: 0x44; STATREG: 0x10; ISREG: 0xc4
CFIREG: 0x80; CNTLREG1-4: 0x57; 0x40; 0x18; 0x44
DMACMD: 0x00; DMASTC: 0x0400; DMASPA: 0x1775c00
DMAWBC: 0x0000; DMAWAC: 0x1776000; DMASTATUS: 0x00
---------------------------------------------------------
scsi0: aborting disconnected command

HEEEEEEEEEEEEEEEEEEELLLLLLLLLLLP!!!!!!!