IJ25443: SLOW TCP PERFORMANCE WITH VIRTUAL ETHERNET ADAPTER AND LARGESENDAPPLIES TO AIX 7100-05

APAR status

• Closed as program error.

Error description

• **************************************************************
  * USERS AFFECTED:
  * Systems running the AIX 7100-05-06-2015 or
  * 7100-05-06-2016 Technology Level with
  * devices.vdevice.IBM.l-lan.rte at the 7.1.5.33
  * level.
    **************************************************************
  * ERROR DESCRIPTION:
  * The Virtual Ethernet Adapter can cause a significant
  * degradation in TCP performance for largesend packets.
  *
  * This issue can be seen with VIOS (serving any AIX, IBMi, or
  * Linux client LPAR) running the affected VIOS levels below.
  * It can also be seen with any AIX client LPAR running the
  * affected AIX levels below (regardless of the VIOS level).
  * This issue only occurs when the client LPARS are configured
  * for largesend traffic or VIOS is configured for largereceive
  * traffic.
    **************************************************************
  * RECOMMENDATION:
  * Install APAR IJ25443.
  * Prior to fix availability, an interim fix is available from
  * either
  * ftp://aix.software.ibm.com/aix/ifixes/ij25443/
  * https://aix.software.ibm.com/aix/ifixes/ij25443/
  * Installation of the ifix requires a reboot.
    **************************************************************
  

Local fix

• Disable PLSO:
  
  Either disable mtu_bypass:
  # chdev -l enX -a mtu_bypass=off
  
  or disable PLSO on the VEA or trunk VEA:
  # chdev -l entX -a platform_lso=no
  

Problem summary

• Customer may experience very slow TCP performance when Platform
  Large Send is enabled on the network interface and the traffic
  is VLAN tagged.
  

Problem conclusion

• Fix ethernet header length calculation for VLAN tagged case.
  

Temporary fix

•   *********
    * HIPER *
    *********
  

Comments

• 6100-09 - use AIX APAR IJ25442
  7100-05 - use AIX APAR IJ25443
  7200-04 - use AIX APAR IJ25390
  

APAR Information

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

  IJ25390

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

Fix information

• Fixed component name

  AIX V7.1

• Fixed component ID

  5765H4000

Applicable component levels

• R710 PSY U885073

     UP20/07/10 I 1000 Ž