Friday, July 29, 2016

Linux kernel 4.7 released

In Linux kernel 4.7 (available here), we improved usability of the kvm_stat tool for z Systems, introducing (among others) new option -p to filter by process ID.

Using kvm_stat, one can monitor e.g. the number of SIE exits or specific diags to investigate performance issues:
  kvm statistics - summary

   Event                                        Total Current
   kvm_s390_sie_enter                          621113      96
   kvm_s390_sie_exit                           621113      96
   kvm_vcpu_wakeup                             231054      69
   kvm_s390_intercept_instruction              187720      24
   kvm_halt_poll_ns                            131133      15
   kvm_s390_handle_diag                         64543      12
   kvm_userspace_exit                            1427      11
   kvm_s390_handle_sigp                        121746       1
   kvm_set_irq                                 154402       0
   kvm_s390_handle_sigp_pei                     18407       0
   kvm_s390_handle_stsi                            12       0
   kvm_s390_handle_stfl                             1       0
Use option -p to further investigate specific QEMU processes to identify the potential culprits:
  $ ./kvm_stat -p 4304 -1 | grep kvm_s390_sie
  kvm_s390_sie_enter                              3985      3985
  kvm_s390_sie_exit                               3985      3985
  kvm_s390_sie_fault                                 0         0

Wednesday, July 13, 2016

Webinar: KVM for z Systems Performance

Abstract: KVM for IBM z Systems performance has not been presented at conferences before. This session covers performance aspects of the KVM host, virtual devices, and considerations for guest definitions to reach certain performance levels. It will also give examples how to monitor host and guest.
Note: It is not intended to compare KVM for IBM z Systems to other hypervisors.

Speaker: Martin Kammerer, Manager Linux on z Systems Performance Evaluation, IBM Germany

Audience: IT Managers, IT Architects, System Administrators

Date: Wednesday, July 20, 2016
Time: 11:00 AM EST / New York, 4:00 PM UK, 5:00 PM CET / Germany
Duration: 75 minutes

Registration: You can register here. After registering, you will receive a confirmation email containing information about joining the webinar.

Replay & Archive
: All sessions are recorded. For the archive as well as a replay and handout of this session (available by July 25, 2016), as well as all previous webcasts please visit

Contact: Please direct any questions to Stephanie Gherghe at

Friday, July 8, 2016

KVM on z Documentation References

The amount of documentation provided in the IBM Knowledge Center can at times be overwhelming. Therefore, this entry will provide some general guidance.
See here for a continuously updated version of this entry.

The documentation for KVM on z (see overall entry point here) is grouped under these categories:
For white papers, Redbooks, live virtual classes, and more, check out the materials related to virtualization on z Systems available here.

In addition, here is a document listing the recommended limits when running KVM on z Systems. It is aimed at the KVM for IBM z product, but also provides a good starting point when running other flavors of KVM on z.

Finally, documentation and pointers on ICM (IBM Cloud Manager, IBM's OpenStack-based product) can be found here.