IJ39013: XW LOCK INTRODUCED IN 1042935 SEEK_DATA CAUSES PERFORMANCE ISSUE

APAR status

• Closed as program error.

Error description

• The customer saw a performance issue since upgrading to
  GPFS 5.1. which appears to be related to an XW lock on
  seek.
  

Local fix

Problem summary

• In some large-scale deployment, high concurrent
  lseek(SEEK_HOLE) calls to a specific file may
  cause performance degradation.
  

Problem conclusion

• This problem is fixed in 5.1.2 PTF 5
  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 lseek(SEEK_HOLE)
  
  Work around:
  If the lseek(SEEK_HOLE) is being invoked from a grep CLI,
  the '-a' option can bypass the lseek(SEEK_HOLE) call.
  Problem trigger:
  High concurrent lseek(SEEK_HOLE) calls on the same file
  Symptom:
  Performance Impact/Degradation
  Platforms affected:
  ALL Linux OS environments
  Functional Area affected:
  All Scale Users
  Customer Impact:
  Suggested
  

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