IJ37260: AVOID OVERHEAD FOR PERMISSION CHECKS WITH MODE BITS

APAR status

• Closed as program error.

Error description

• Linux kernel v3.1 introduced a change to retrieve a file
  system ACL for each permission check. The change
  introduced
  overhead in concurrent path lookups heavy workloads.
  

Local fix

Problem summary

• Linux kernel v3.1 introduced a change to retrieve a file
  system ACL for each permission check. The change
  introduced
  overhead in concurrent path lookups heavy workloads.
  

Problem conclusion

• This problem is fixed in 5.1.2  PTF 3
  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:
  
  This fix addresses the performance problem in these specific
  concurrent lookup workloads on file systems with only modebits
  permission's.
  
  Work Around:
  The only possible work around would be to
  reduce the number of concurrent lookups.
  
  Problem trigger:
  Lots of lookups to the file system. One
  known case is setting LD_LIBRARY_PATH to directories on a GPFS
  file system on zLinux. The zLinux dynamic linker issues a much
  higher number of lookups for each entry in LD_LIBRARY_PATH,
  making this scenario more likely to occur.
  
  Symptom: Performance Impact/Degradation
  
  Platforms affected: ALL Linux OS environments
  
  Functional Area affected: All Scale Users
  
  Customer Impact: High Importance
  

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