LI76907: SNA SLOWS DRASTICALLY WHEN ANOTHER PROCESS TAKES CPU

Communications Server for Linux, Version 6.4 -- Latest Fixpack

APAR status

• Closed as program error.

Error description

• Communications Server for Linux on System Z
  -------------------------------------------
  On a multi-processor system, if one or more processors have high
  CPU usage from one or more other processes, the LiS processes of
  Communications Server appear to not get any CPU time, even those
  that are running on processors that are not under high usage.
  This drastically slows SNA communications, and may even cause
  link failures.
  

Local fix

• Assign only one processor to the system.
  

Problem summary

• Each LiS process is tied to a specific processor. However, the
  processes communicate with each other, so if one becomes
  CPU-starved, then the rest have to wait on that one, so they all
  appear to become slowed.
  

Problem conclusion

• Code has been changed to un-tie the LiS processes from specific
  processors. Each LiS process is started with an affinity for a
  specific processor, but is now allowed to float to other
  processors when necessary.
  

Temporary fix

• LiS patch
  

Comments

APAR Information

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

  LI76850

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

Fix information

• Fixed component name

  CS FOR LINUX

• Fixed component ID

  5724I3300

Applicable component levels

• R640 PSY