gdth / SCSI read performance issues (2.2.19 and 2.4.10)

From: Marinos Yannikos (mjy@geizhals.at)
Date: Wed Oct 24 2001 - 07:22:16 EST


Hi,

our brand-new ICP GDT8523RZ controller with 6 disks peaks out at
45MB/s under 2.4.10, while with 2.2.19 it reaches 85MB/s (seq.
read performance). It should realistically be able to reach
at least 150-200MB/s in this configuration (RAID-5, 6 disks,
it's a 64-bit 66MHz PCI card). It's in a dual P3-1GHz box with
Tyan 2510NG board. Sequential write performance is OK with both
kernels, it's higher than the read performance on 2.4.10 (60MB/s).

Under 2.4.10, when I test the performance with a simple program
that just read()'s 16MB blocks from /dev/sda, both CPUs report
40-50% System time usage. 2.2.19 reports ~20% for one CPU (and
better performance).

Is there anything that can be done about this? It seems like a
serious performance problem either with the gdth driver or the
kernel and it renders this neat controller rather ineffective.

Regards,
-mjy
[please CC: answers]

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