Re: Fedora 14 [was 11] s390x emulator

[Mark Wielaard <mjw at redhat dot com>]

Hi,

Just a few notes, since I finally tried this.
Thanks for pointing it out.

On Wed, 2009-08-19 at 13:00 -0500, David Smith wrote:
> The Fedora s390x team has published a f11 s390x hercules emulator image.
>  Since that message was sent, there was a second image published, called
> 'f11-s390x-20090716.img.bz2' that you'll find in
> <http://secondary.fedoraproject.org/pub/alt/spins/S390/>.

There is now also a f14 setup. You will need
fedora-14-s390x-20100927.img.bz2 which uncompresses into a large volume
that has enough space to install all the debuginfo into (the smaller
fedora-14-s390x.img file needs more tweaking and also seems to default
to yum rawhide repos - I had some troubles with that update, so I
abandoned it).

> I've taken that image, booted it, and done some systemtap testing with
> it.  Here's what I've found.
> 
> - Setup: Once your host system setup is done, setting the the s390x
> guest image is normal for any f11 system.  You'll need to use yum to
> install the various packages systemtap needs for development and test.
> 
> Note that there isn't a s390x yum debuginfo repository, so you'll have
> to download the kernel's debuginfo packages from the s390x project's
> koji instance: <http://s390.koji.fedoraproject.org/koji/>

The fedora-14-s390x-20100927.img.bz2 is setup to have normal debuginfo
yum. So if you yum install yum-utils you can just use debuginfo-install.

> - Speed:  As you can imagine, the emulated s390x system is slow, very
> slow.  But, with patience, it is usable.  Note that yum seems to be
> extremely slow.

It definitely helps to allocate a lot of memory to the virtual machine,
and if you have multiple cpus/cores to allocate a couple in
hercules.cnf:

MAINSIZE  2560
NUMCPU    4

And make sure to disable the cpuplugd service in the guest. It will
happily disable CPUs it thinks aren't in use, but never seems to give
them back.

> - Systemtap: Systemtap seems to generally work on the emulated s390x
> system.  I've worked with kernel is 2.6.29.5-191.fc11.s390x (after a yum
> update), so it is much more recent than a rhel5 kernel.

The latest s390x f14 kernel is 2.6.35.6-45.fc14.s390x

> I was never able to get a full systemtap testsuite run completed.  The
> first problem I ran into was I kept getting timeouts.  After an increase
> of 20x on all timeout values, I didn't get timeouts anymore, but the
> testsuite would just hang after awhile.

After 38 hours I had a complete make installcheck run. It didn't hang.
But it did include a lot of timeouts indeed. Still the results were not
great, but could be worse...

# of expected passes            2162
# of unexpected failures        640
# of unexpected successes       7
# of expected failures          273
# of untested testcases         71
# of unsupported tests          6

> So, from a systemtap point of view, what could you use this for?
> 
> - an easy way to test for compilation errors on an s390x
> 
> - a good way to test an individual systemtap testcase/feature

Yeah, it definitely can be used for some quick tests, but it is some
work to set it up and it is slow. So don't try to use it for "real
work".

Cheers,

Mark