As part of the update to TOSS 4.8-7 in early February 2025, we are isolating system process on CTS-2 clusters (bengal, dane, rzHound) to the low-numbered hardware threads (0-111) in order to minimize system noise on the high-numbered hardware threads (112-223). Our mpibind plugin will automatically bind user processes to these high-numbered hardware threads, so most users will not need to do anything to take advantage of the low-noise configuration.

If you explicitly disable mpibind for your jobs with --mpibind=off in order to do your own binding and have processes bound to the low-numbered hardware threads, you may see some performance degradation from sharing the threads with system processes. We recommend that you try binding your processes to the high-numbered hardware threads if you are experiencing performance issues.

Please contact the LC Hotline (lc-hotline@llnl.gov or 925-422-4531, option 1) if you have any questions about this.