Deadline servers as a realtime throttling replacement

Posted Jun 17, 2023 8:55 UTC (Sat) by anton (subscriber, #25547)
In reply to: Deadline servers as a realtime throttling replacement by Fowl
Parent article: Deadline servers as a realtime throttling replacement

If the system is competently cooled, it reaches the power limit before it reaches the thermal limit, and it reaches the thermal limit before it starts throttling. The answer to reaching the power limit or thermal limit is to lower the clock rate and the voltage, which means that the power consumption is reduced more than the performance. OTOH, throttling is an emergency mechanism that just skips clock cycles without reducing voltage (or reducing the actual clock rate, although the effective clock is reduced).

Running a CPU 95% of the time (and halting it for 5%) is similar to throttling in its effect on power consumption. When the CPU is at the power or thermal limit, it will generally perform more work if you let it run all the time than if you let it run only 95% of the time. "More work" will not be 1/0.95 times as much, but it will be >1.