Re: Linux 2.6.16 - SATA read performance drop ~50% on Intel 82801GB/GR/GH

[Linda Walsh <lkml@tlinx.org>]

Andreas Schnaiter wrote:
> The two affected disks are connected to the Intel 82801GB/GR/GH (ICH7 Family)  
> Serial ATA Controller.
> Disks on the Silicon Image/Intel IDE Controllers are not affected.
>
> Linux 2.6.15.7
> ---
> # time dd if=/benchfile of=/dev/null bs=1M
> 8192+0 records in, 8192+0 records out
> 8589934592 bytes (8.6 GB) copied, 130.547 seconds, 65.8 MB/s
> real	2m10.670s user	0m0.023s sys	0m14.238s
>
> Linux 2.6.16.2
> ---
> # time dd if=/benchfile of=/dev/null bs=1M
> 8192+0 records in, 8192+0 records out
> 8589934592 bytes (8.6 GB) copied, 302.452 seconds, 28.4 MB/s
> real	5m3.100s user	0m0.021s sys	0m40.521s
---
    Slightly echoing Jeff G's question, but rephrasing for read,
could you try a read on the actual device?  I.e. without
destroying your partition, you could try a direct read
from the device:

     time dd if=/dev/sda of=/dev/null bs=1M count=8192.

BTW, how much memory do you have on the system?

    Not that I have know much about block-i/o, but it
might narrow things down.

    Have you tried the tests in single-user or run-level 1 to
help rule out other noise?

Linda