Re: Very bad interactivity with 2.6.0 and SCSI disks (aic7xxx)

[Andrew Morton <akpm@osdl.org>]

Stefan Foerster <stefan@stefan-foerster.de> wrote:
>
> * Andrew Morton <akpm@osdl.org> wrote:
> > Stefan Foerster <stefan@stefan-foerster.de> wrote:
> > A kernel profile would be needed to diagnose this.  You could use
> > readprofile, but as it may be an interrupt problem, the NMI-based oprofile
> > output would be better.
> 
> Is this procedure documented anywhere?
> 

Documentation/basic_profiling.txt and oprofile.sourceforge.net.

oprofile is hard to get going and they seem to keep on changing things.

A quick primer would be:

- download the userspace tools, carefully read the INSTALL and README
  files.

- You need to do ./configure --with-kernel-support (something like that).

- build and install.


>From my notes, for a P4:

opcontrol --setup --vmlinux=/boot/vmlinux --ctr0-count=600000 --ctr0-unit-mask=1  --ctr0-event=GLOBAL_POWER_EVENTS 

For a PIII:

opcontrol --setup --vmlinux=/boot/vmlinux --ctr0-count=600000 --ctr0-event=CPU_CLK_UNHALTED

Then:

opcontrol --shutdown
rm -rf /var/lib/oprofile
opcontrol --start-daemon
opcontrol --start
<run test>
opcontrol --stop

oprofpp -l /boot/vmlinux
oprofpp -Lo /boot/vmlinux > /tmp/1


I use this script.

#!/bin/sh
sudo opcontrol --stop
sudo opcontrol --shutdown
sudo rm -rf /var/lib/oprofile
sudo opcontrol --start-daemon
sudo opcontrol --start
time $@
sudo opcontrol --stop
sudo opcontrol --shutdown