IJ29943: CONTENTION ON INODECACHEOBJMUTEX IMPACTS THE WRITE PERFORMANCE

APAR status

• Closed as program error.

Error description

• Customer may hit performance issue from Ganesha client
  IO.
  One reason of this write performance degradation issue
  is the contention on the InodeCacheObjMutex, after
  customer upgraded to 5.0.4.3 from 4.2.3.9. One
  contribution for such contention was added by QoS fileset
  support code since 5.0.3.
  
  Reported In:
  Spectrum Scale 5.0.4.3
  
  Known Impact:
  Caused contention that impact performance
  

Local fix

• disable prefetch for write via:
  "mmchconfig prefetchAggressivenessWrite=0 -i"
  

Problem summary

• When there are  many threads doing sync writes through
  the same file descriptor, a contention on
  inodeCacheOjbMutex between them could impact the
  performance of writes.
  

Problem conclusion

• Benefits of the solution:
  Better performance for sync writes
  
  Work around:
  Enable the config parameter "prefetchAggressisvenessWrite"
  to work around the problem if the workload is only doing sync
  writes.
  
  Problem trigger:
  Multiple threads are doing sync writes on the
  same opened file concurrently.
  
  Symptom:
  Sync write performance becomes bad
  after upgrading to 5.0.x.
  
  Platforms affected:
  All Operating Systems
  
  Functional Area affected:
  Sync writes
  
  Customer Impact:
  Suggested
  

Temporary fix

Comments

APAR Information

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

  IJ29447

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

  IJ30125

Fix information

• Fixed component name

  SPEC SCALE STD

• Fixed component ID

  5737F33AP

Applicable component levels