HP Smart Array P400 slow in kernel.org 2.6.29, fast in 2.6.24.2
 

I'm noticing a slow down in disk reads when booting from 2.6.29.4 kernel. The older kernel has a faster read time.

There are massive differences in the kernels so doing a diff is not very helpful.

Any suggestions on perf tuning for this type of device?

I'm using kernel.org kernels

2.6.24.2
# hdparm -tT /dev/cciss/c0d0
/dev/cciss/c0d0:
Timing cached reads: 10508 MB in 2.00 seconds = 5256.20 MB/sec
Timing buffered disk reads: 1274 MB in 3.01 seconds = 423.94 MB/sec

2.6.29.4
# hdparm -tT /dev/cciss/c0d0
/dev/cciss/c0d0:
Timing cached reads: 34272 MB in 2.00 seconds = 17156.82 MB/sec
Timing buffered disk reads: 242 MB in 3.02 seconds = 80.26 MB/sec

This is more background reading than an answer, but you might like to read this, particularly the 7-Zip bit

http://www.phoronix.com/scan.php?pag...nchmarks&num=2

there may be a more useful answer forthcoming if you say something about the filesystems in use and the mount options (but probably not from me...that was my limit!)