IJ43542: IMPROVE THE PERFORMANCE FOR THE CONCURRENT READS ON SMALL FILES OR APPEND WRITES FROM MULTIPLE THREADS

APAR status

• Closed as program error.

Error description

• When reading the small files containing single data
  block from multiple threads, these threads could be
  interlocked with each other on the prefetch check,
  although they are reading different small files, then
  the contention on the prefechListMutex cause the performance
  degradation. A similar issue could happen on concurrent
  append writes to files from multiple threads.
  

Local fix

• Downgrade the configuration parameter
  "prefetchAggressiveness" to the 1.
  

Problem summary

• When reading the small files containing single data
  block from multiple threads, these threads could be
  interlocked with each other on the prefetch check,
  although they are reading different small files, then
  the contention on the prefechListMutex cause the performance
  degradation. A similar issue could happen on concurrent
  append writes to files from multiple threads.
  

Problem conclusion

• This problem is fixed in 5.1.2 PTF 8
  To see all Spectrum Scale APARs and
  their respective fix solutions refer to page
  https://public.dhe.ibm.com/storage/spectrumscale/spectrum_scale_
  apars.html
  
  Benefits of the solution:
  Improve the performance of reads on small files
  and append writes on files.
  
  Work around:
  Downgrade the configuration parameter
  "prefetchAggressiveness" to the 1.
  
  Problem trigger:
  Concurrent reads on different small
  files from different threads.
  
  Symptom:  Performance issue on read or append write.
  
  Platforms affected: All Operating Systems
  
  Functional Area affected:  All Scale Users
  
  Customer Impact: Important
  

Temporary fix

Comments

APAR Information

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

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

Fix information

• Fixed component name

  SPEC SCALE STD

• Fixed component ID

  5737F33AP

Applicable component levels