High %sys CPU usage in tg_load_down when running a large number of independent (own SID) processes

Solution Verified - Updated -

Issue

  • Noticed degradation in performance after upgrading from RHEL 7.2 to 7.3.
  • Same load with RHEL7.2 kernel does not reproduce the issue, but when running with RHEL7.3 kernel noticed spikes at system level. tg_load_down appears in perf top, noticeable increase in both %sys and %si.

Environment

  • Red Hat Enterprise Linux 7.3 and 7.4
  • All kernels from 3.10.0-514 and 3.10.0-693 series.

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