VM66467: PCI GUEST INSTRUCTION IMPROVEMENTS

Obtain the fix for this APAR.

APAR status

• Closed as unreproducible in next release.

Error description

• Guest workload with a high number of certain instructions to PCI
  devices can see decreased performance.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of z/VM PCI Functions              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  There were some cases during z/VM's simulation of guest
  PCI instructions where unnecessary real
  instructions were being issued on behalf of the guest.
  This results in decreased performance and throughput of guest
  workloads using PCI functions.
  

Problem conclusion

Temporary fix

• FOR RELEASE VM/ESA CP/ESA R720 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

• PCI simulation for guest
  instructions was updated to check for cases where a host
  instruction does not need to be issued on behalf of the guest.
  This allows the real instructions to be skipped which result in
  improved performance of guest PCI workloads.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UM35824

Modules/Macros

• HCPPCH   HCPPCK
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R720 PSY UM35824

     UP21/02/23 P 2102 ¢

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.