Re: [ck] 2.6.16-ck1

[Wu Fengguang <wfg@mail.ustc.edu.cn>]

Hi Rodney,

Thanks for your testing :)

On Thu, Mar 23, 2006 at 05:31:18AM -0600, Rodney Gordon II wrote:
> Adaptive readahead: I had probs with this before, and I still do.. On
> a desktop if you have odd problems (nothing responding for SECONDS,
> very slow disk I/O during heavy I/O, etc..) disable it.

Your problem on I/O latency with ara can be tracked down with the help
of Ingo's latency tracing patch. It goes like this:

1) download
http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.16.tar.bz2
http://www.vanheusden.com/ara/adaptive-readahead-11-2.6.16-rc6.patch.gz
http://people.redhat.com/mingo/latency-tracing-patches/latency-tracing-v2.6.16.patch

2)
tar jxf linux-2.6.16.tar.bz2
gunzip adaptive-readahead-11-2.6.16-rc6.patch.gz
cd linux-2.6.16
patch -p1 < ../adaptive-readahead-11-2.6.16-rc6.patch
patch -p1 < ../latency-tracing-v2.6.16.patch

3) compile kernel with Adaptive readahead support
4) boot with the new kernel, and run
echo 0 > /proc/sys/kernel/preempt_max_latency
5) feel some latency problems
6) report the content of /proc/latency_trace

Thanks,
Wu
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