Bug Report: Reduced disk performance in 2.6.1

Bug Report: Reduced disk performance in 2.6.1

[Ashton Mills]

Following the bug reporting guide at www.kernel.org.

Sending to linux-kernel@vger.kernel.org because I don't know where the
problem lies, I've eliminated two areas (detailed below).

PROBLEM:

Stock 2.6.1 kernel shows reduced disk performance compared to stock 2.6.0.

DESCRIPTION:

2.6.0 -- hdparm -Tt shows:

~70 M/s for a single drive
~110 M/s for 2-drive software RAID 0 array

2.6.1 -- hdparm -Tt shows:

~60 M/s for single drive
~90 M/s for 2-drive software RAID 0 array

Kernel configuration file the same -- used .config from 2.6.0 with make
oldconfig

Reproducible: yes. Results remain consistent between the two kernels.

This is the only change to the system. No other software or hardware was
changed, just a straight kernel upgrade.

Relevant specs:

Athlon-XP 2800+
1024M RAM
Adaptec 29160
Two Maxtor 10k RPM U160 SCSI drives in md software RAID 0 array

Linux version 2.6.1 (root@Agamemnon) (gcc version 3.3.2 20031218 (Gentoo
Linux 3.3.2-r5, propolice-3.3-7))

PROGRESS:

Patched 2.6.1 with the 2.6.0 aic7xxx SCSI driver in case it was a result of
the new .36 version of the driver.
Result: problem remains

Patched 2.6.1 with the 2.6.0 md driver, since that was also shown to be
updated in 2.6.1
Result: problem remains

So, it doesn't appear to be a SCSI or md driver issue. Don't know where to
go from here, reporting as bug.