PK46764: NEW FUNCTION - DYNAMIC LAN IDLE (TCP/IP PART) (SEE APAR OA21405 FOR OTHER PART OF CODE)

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Dynamic LAN Idle
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users with IBM System z9 EC or z9 BC and *
  *                 the OSA-Express2 feature with dynamic LAN    *
  *                 idle timer support.                          *
  *                                                              *
  *                                                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: See Problem Summary                     *
  *                                                              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
    OSA supports an inbound "blocking" (or packing) function over
  the QDIO interface.  This function affects how long OSA will
  hold packets before "presenting" those packets to the host. Here
  "presenting" means assigning the read buffer to the host, which
  is a matter of updating the state of the host buffer to host
  owned. In most cases this same action will result in an
  interrupt to the host for this QDIO data device.  Therefore,
  this function indirectly affects the QDIO interrupt processing
  (i.e. how frequent the host will be interrupted, and the
  payload per interrupt).
    This function is referred to as the OSA "LAN Idle timer".
  Today the host can pass various time intervals to OSA when the
  QDIO data device is activated. In the z/OS case, the system
  administrator can adjust this setting. However, the setting is
  static and can not be changed unless the connection to OSA is
  terminated (device is stopped) and re-established (restart the
  device).
    Currently the user can not directly configure explicit LAN
  Idle settings.  Instead the user provides a constant value to
  OSA which represented the best "compromise" setting.  In the
  TCP/IP profile the user can define a LAN Idle setting for an
  OSA Express in QDIO mode device. This is performed by
  specifying the TCP/IP profile INBPERF parameter with one of the
  following options:
        o MINCPU setting
                 OSA should increase packet hold time. Holding
                 packets longer minimizes CPU utilization by
                 decreasing interrupt frequency and providing a
                 better payload per interrupt
        o MINLATENCY setting
                 OSA should decrease packet hold time.
                 Presenting packets to host sooner reduce
                 network latency (but drive up CPU utilization
                 by causing more frequent interrupts and a
                 smaller payload per interrupt)
        o BALANCED Setting (default)
                 CS would compromise and set timer interval
                 values that split the difference in the above
                 two settings
  
    To assist in reducing latency for light interactive workloads,
  a new INBPERF parameter option of DYNAMIC  will now be
  permitted. This new configurable setting allows the TCP/IP
  stack to dynamically calculate the best values. These
  dynamically calculated values will then be sent to the OSA and
  it will begin actively using the new setting(s).  With this
  model ("dynamic user setting"), the host stack (device driver)
  will heuristically adjust the settings based on system
  environmental conditions (inbound work load volume, CPU
  utilization, traffic patterns, etc.), and OSA will adapt to the
  changes.
  
    Performance studies have shown network latency improvements
  in environments where the CEC is under low utilization of up to
  35% by tuning the LAN Idle timer within the OSA Express2 using
  a dynamic algorithm that takes workload characteristics. This
  dynamic algorithm involves taking the current default
  inter-packet gap of 40 microseconds to as low as 1 microsecond.
  
    For the dynamic LAN idle function to be utilized an IBM System
  z9 EC or z9 BC is required, and the OSA-Express2 feature must
  have dynamic LAN idle timer support. See the 2094DEVICE
  Preventive Service Planning (PSP) and the 2096DEVICE
  Preventive Service Planning (PSP) buckets for more information.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• D/T2096
  

Temporary fix

Comments

• OSA supports an inbound "blocking" (or packing) function over
  the QDIO interface.  This function affects how long OSA will
  hold packets before "presenting" those packets to the host. Here
  "presenting" means assigning the read buffer to the host, which
  is a matter of updating the state of the host buffer to host
  owned. In most cases this same action will result in an
  interrupt to the host for this QDIO data device.  Therefore,
  this function indirectly affects the QDIO interrupt processing
  (i.e. how frequent the host will be interrupted, and the
  payload per interrupt).
    This function is referred to as the OSA "LAN Idle timer".
  Today the host can pass various time intervals to OSA when the
  QDIO data device is activated. In the z/OS case, the system
  administrator can adjust this setting. However, the setting is
  static and can not be changed unless the connection to OSA is
  terminated (device is stopped) and re-established (restart the
  device).
    Currently the user can not directly configure explicit LAN
  Idle settings.  Instead the user provides a constant value to
  OSA which represented the best "compromise" setting.  In the
  TCP/IP profile the user can define a LAN Idle setting for an
  OSA Express in QDIO mode device. This is performed by
  specifying the TCP/IP profile INBPERF parameter with one of the
  following options:
        o MINCPU setting
                 OSA should increase packet hold time. Holding
                 packets longer minimizes CPU utilization by
                 decreasing interrupt frequency and providing a
                 better payload per interrupt
        o MINLATENCY setting
                 OSA should decrease packet hold time.
                 Presenting packets to host sooner reduce
                 network latency (but drive up CPU utilization
                 by causing more frequent interrupts and a
                 smaller payload per interrupt)
        o BALANCED Setting (default)
                 CS would compromise and set timer interval
                 values that split the difference in the above
                 two settings
  
    To assist in reducing latency for light interactive workloads,
  a new INBPERF parameter option of DYNAMIC  will now be
  permitted. This new configurable setting allows the TCP/IP
  stack to dynamically calculate the best values. These
  dynamically calculated values will then be sent to the OSA and
  it will begin actively using the new setting(s).  With this
  model ("dynamic user setting"), the host stack (device driver)
  will heuristically adjust the settings based on system
  environmental conditions (inbound work load volume, CPU
  utilization, traffic patterns, etc.), and OSA will adapt to the
  changes.
  
    Performance studies have shown network latency improvements
  in environments where the CEC is under low utilization of up to
  35% by tuning the LAN Idle timer within the OSA Express2 using
  a dynamic algorithm that takes workload characteristics. This
  dynamic algorithm involves taking the current default
  inter-packet gap of 40 microseconds to as low as 1 microsecond.
  
    For the dynamic LAN idle function to be utilized an IBM System
  z9 EC or z9 BC is required, and the OSA-Express2 feature must
  have dynamic LAN idle timer support. See the 2094DEVICE
  Preventive Service Planning (PSP) and the 2096DEVICE
  Preventive Service Planning (PSP) buckets for more information.
  

APAR Information

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

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

  UK27017 UK27018

Modules/Macros

• EZACDMO1 EZACDNE0 EZACDNE6 EZACFPAR EZACFPSC
  EZACFPTK EZACFPV6 EZACFYAC EZASAIFH EZASAIOC EZASNSM2 EZBCTFME
  EZBDGDAT EZBDGPRF EZBDIF   EZBIFINB EZBIFIND EZBIFIN2 EZBIFIOC
  EZBIFMDF EZBIFSTC EZBITCOM EZBITCVT EZBITIN2 EZBITMES EZBITMST
  EZBITTRC EZBITTUB EZBZIPA  HHHZTSDX IOCTLI   PLAZTSDX YACCFYAC
  ZZTOIPIO
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R180 PSY UK27017

     UP07/08/14 P F708

• R189 PSY UK27018

     UP07/08/14 P F708

Fix is available

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