During recent large scale benchmarking activities, we were seeing excessive %sys CPU time that negatively impacted scaling of the application.
We have found that a lot of the time was spent in the localtime() system call due to the TZ environment variable not being set. A simple test routine was created to confirm the observation, and the elapse time differences and CPU resources needed with TZ set versus TZ not set were astonishing. It was discovered that the inherit use of stat() system calls to /etc/local_time from localtime() are very expensive when TZ is not set.
InterSystems highly recommends confirming in any Linux installation whether x86 or Linux on Power that the TZ environment variable is set appropriately for optimal performance. For more details see: "man tzset"