horrible performance with newer kernels on PE2650 with PERC3D/i

[Dominik L. Borkowski]

Hello,

We have observed this problem months ago, but waiting for possible fix never 
produced any results. It seems that starting around kernel 2.6.22, the I/O 
performance on PE2650's with PERC3D/i controllers [aacraid driver], seems to 
be shot completely. 

The issue occurs on all 5 PE2650's that we have with this particular 
controller, not on any other PE2650's. Machines are up-to-date in terms of 
firmware, including PERC 2.8.1.7692 firmware. Problem occurs on vanilla 
kernels from kernel.org, and on distro-patched kernels [for example opensuse 
11.1]. 

Sample dd sessions:

# time dd if=/dev/zero of=bigfile bs=1M count=100 conv=fsync
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 15.2222 s, 6.9 MB/s

real    0m15.227s
user    0m0.004s
sys     0m0.580s

# time dd if=/dev/zero of=bigfile bs=1M count=1000 conv=fsync
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 69.2139 s, 15.1 MB/s

real    1m9.281s
user    0m0.016s
sys     0m6.904s

I was wondering, has anybody else run into this problem?  We haven't been able 
to find a fix so far, and any hints would be greatly appreciated.

--
dom