The first thing to do is to set up the machine so that
any time a process segfaults, a coredump is produced and
saved. Following tips on
I added the following lines to
# Create coredumps in /var/log/core mkdir -p /var/log/core chmod 0777 /var/log/core echo "/var/log/core/core.%e.%t.%p" > /proc/sys/kernel/core_pattern echo 0 > /proc/sys/kernel/core_uses_pid
These lines cause coredump files to be captured centrally in
a single directory (
/var/log/core) with a standardised
naming scheme (eg.
However they don't yet ensure that coredumps will actually be
produced. To change that we need to edit two more files. In
/etc/security/limits.conf, add these lines:
* hard core unlimited * soft core unlimited
/etc/profile you may need to comment out
#ulimit -S -c 0 > /dev/null 2>&1
(why that is there I have no idea). If you log out and log in again you should see:
$ ulimit -Hc unlimited $ ulimit -Sc unlimited
and the same should happen if you 'su' to root or log in as root.
Note that unfortunately this doesn't make coredumps happen for init scripts. They aren't run as a logged in user. So after booting the machine you should restart any services for which you want coredumps. In particular:
One way to stress a Xen machine is to start and stop domains. To avoid having to do this manually, we'd like to do it from a script.
First of all you need to create a number of domains. For this testing
they should be Unix-like and they should have a console and be set up
to listen for logins on that console (because we rely on them creating
a login prompt on the console in order to detect that they have fully
booted). I simply created a Fedora Core
6 paravirt guest and cloned its disks to create 4 guests in all.
My guests were called (imaginatively)
It should be possible to boot the guest and wait for it to come up fully by doing:
# /usr/sbin/xm start fc6 # ./waitlogin.sh fc6
If everything is working well then the
command should not return until the guest has finished booting up.
Similarly to shut it down and wait until it has shut down fully:
# /usr/sbin/xm shutdown fc6 # ./waitshutdown.sh fc6
You are now ready to begin stress testing. Start four terminals and in each one do:
# ./startstop.sh guestname
where guestname is
or whatever you called your guests.
On x86-64 the kernel prints a message whenever a segfault happens so the easiest way to look out for them is to do:
$ watch -n 10 'dmesg | grep seg'
You can also keep an eye on the
If you find a coredump, please report the problem on Bugzilla.
For real load testing, I also keep a copy of the latest Linux kernel around, and I use a simple script to continuously rebuild it:
$ cd /usr/src/linux-184.108.40.206/ $ while true; do make -j 4; make clean; done
-j 4 with the number of CPU cores
that you have in the system (excluding "hyperthreads" which
you should probably turn off anyway).
$Id: index.html,v 1.1 2007/05/17 10:54:29 rjones Exp $