July 26, 2013

z/VM 6.3

After a long waiting time IBM released the latest version of z/VM. Now there is way more information available than just the little bit I described in my preview
The major items haven't changed from the preview - it's CPU scalability using Hiperdispatch and support for 1 TB per z/VM instance.

The announcement also has a statement of direction for z/VM 5.4.  Basically it says that the current System z generation (EC12 /BC12) will be the last one that's supported with z/VM 5.4. And support for z/VM 5.4 will end whenever the z9 hardware support ends. So it's time to plan for the upgrade to z/VM 6.3.

(updated 9/21/2013) 

July 24, 2013

Large Systems Performance Reference (LSPR) for zLinux

The Large Systems Performance Reference (LSPR) published by IBM has also a Linux workload included. There you can get a first impression of the relative performance about new System z processors.
More details can then be found in the z Processor Capacity Reference (zPCR).

July 16, 2013

Fedora 19 for IBM System z released

The new Fedora 19 release for System z / s390x happened today. Congratulations to the team!

The download is available from the Fedoraproject site and the respective mirrors and known issues  are covered in the wiki.

July 11, 2013

How to determine which kernel level corresponds to which service release for RHEL and SLES

Now and then I get the question - where to find the kernel level or version for a specific service release. And vice versa - I have kernel level x.y.z - what is the respective service level?
Both distributors SUSE as well as Red Hat offer this information on their web sites - even though not quite obvious to find. So here it is as a reference:

July 9, 2013

SLES 11 SP3 released

Today SUSE announced the release of Service Pack 3 for SLES 11. It's been more than 16 months since the last release, so quite some waiting time for new features. This time the kernel level stayed the same, so the upgrade from SLES11 SP2 to SLES11 SP3 should be easier than the one before.  You can find more information on this release here:
SUSE has released the first maintenance web kernel for SP3 (kernel-default-3.0.82-0.7.9.s390x.rpm). It contains more fixes than usual so as always when upgrading and starting, get the latest service installed. 

As more information becomes available I'll update this post. Latest Update 8/6/2013.

Cheat sheet for lock debugging in the Linux kernel

From time to time I'm getting a performance problems that requires identifying the lock in the Linux kernel that causes too much lock contention. The newer kernels are well equipped to help you find that lock. If you can do something that's another question.
The base documentation for that is in the kernel source under Documentation/locking/lockstat.txt. However due to the performance impact of all that tracing this usually is disabled in the distributions. For RHEL 6.4 there is a separate debug kernel that you need to install. Ensure that it's the default IPL/boot kernel or select in the IPL/boot menu.
SLES 11 is more difficult as this requires a  kernel rebuild with CONFIG_LOCK_STATS enabled. You need to contact SUSE service to get a kernel for your system.
If you have the system up with this enabled you should do the following:
  • echo 1 >/proc/sys/kernel/lock_stat
  • run your workload 
  • cat /proc/lock_stat > /tmp/lockreport.txt
  • echo 0 >/proc/sys/kernel/lock_stat
Usually you only need to take a look at the few top locks to find out what's going wrong.