Does soft lockup detection cause a 1-second latency in RHEL5?

Solution Unverified - Updated -

Environment

  • Red Hat Enterprise Linux 5

Issue

  • The following statement appears in an HP whitepaper detailing BIOS setting for low latency systems.
  • Could you please confirm that Red Hat agree with the statement and have no issue with the recommendation?

  • If you could also add in any specific implications of carrying out the recommendation that would be great.

    “Red Hat Enterprise Linux 5 kernel soft lockup detection generates an interrupt every ten seconds. This interrupt results in an approximately one second latency each time it occurs.
The default interval is ten seconds. This interval can be extended to a maximum of 60 seconds by writing the appropriate value to /proc/sys/kernel/softlockup_thresh.
To minimize the impact of this interrupt on applications, adjust the software lockup detection interval.”

Resolution

  • The statement in the HP whitepaper is incorrect. The latency caused by softlockup detection is negligible.
  • The latency when a softlockup is actually detected and reported will depend on the speed of the console device.

Root Cause

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