Comment 25 for bug 620074

(In reply to comment #2)
> I'm also having this problem.
>
> Latest working kernel version: 2.6.18.8 with config:
>
> http://svn.pardus.org.tr/pardus/2007/kernel/kernel/files/pardus-kernel-config.patch
>
> Currently working on 2.6.25.20 with config:
>
> http://svn.pardus.org.tr/pardus/2008/kernel/kernel/files/pardus-kernel-config.patch
>
> Tested also with 2.6.28 and felt no significant performance improvement.
>
> --
>
> During heavy disk IO's like running 'svn up' hogs the system avoiding the
> start
> a new shell, browse on the internet, do some text editing using vim, etc.
>
> For example, after being able to open a text buffer with vim, 4-5 seconds
> delays happens between consecutive search attempts.

You seem to be able to reproduce the bug easily, and have found a non affected kernel version.
Can you git bisect between those kernels to at least isolate the culprit commit?