IV58939: EFFECT POOLBUCKETS CHANGES FROM 2 TO 7 AND AT BOOT APPLIES TO AIX 7100-03

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The out-of-the box value for poolbuckets differs between
  P7 and P8.  This ends up in 3 extra locks/unlocks
  during mbuf Get/Alloc on P8 compared to P7, which
  for some workloads may result in a net penalty.
  Additionally, the poolbuckets network option is not effective
  between values of 2 and 7, or at boot time.  The tunable
  therefore cannot be used on P8 to reduce the number of
  buckets to the P7 value.
  

Local fix

Problem summary

• The out-of-the box value for poolbuckets differs between
  P7 and P8.  This ends up in 3 extra locks/unlocks
  during mbuf Get/Alloc on P8 compared to P7, which
  for some workloads may result in a net penalty.
  Additionally, the poolbuckets network option is not effective
  between values of 2 and 7, or at boot time.  The tunable
  therefore cannot be used on P8 to reduce the number of
  buckets to the P7 value.
  

Problem conclusion

• In the original code, when the "poolbuckets" value was less
  than 7, it would pick the minimum of POOLBUCKETSMAX (7) or
  _system_configuration.smt_threads (which defaults to 4 in P7
  systems and 8 in P8 systems).  The solution retains the
  above behavior for the default case (poolbuckets=1). For all
  other cases it allows the user's choice to take effect. It
  also makes the changes effective at boot time from the next
  reboot, so that the UDP code which uses the value at boot time
  can also pick up the tuned value.
  

Temporary fix

Comments

• 7100-03 - use AIX APAR IV58939
  7100-04 - use AIX APAR IV58875
  

APAR Information

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

  IV58875

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

  U866419

Fix information

• Fixed component name

  AIX V7.1

• Fixed component ID

  5765H4000

Applicable component levels

• R710 PSY U866419

     UP14/05/22 I 1000