When running CPU intensive benchmarks on a typical x86 Linux system, an absolutely quiet system isn't needed for many types of benchmarks that stress only the CPU, L1 and L2 caches, since these resources are core private and so (in the absence of hyperthreading) the currently running thread gets mostly free and unrestricted access to those resources.
There are still many sources of variance, but when mitigated, benchmarks are often very stable: often being repeatable down to the exact cycle, even with lots of stuff running the background.
That goes out the window once your benchmark touches L3 or main memory, as these are shared resources. Anything at all on your system, running concurrently with your benchmark will compete for access to these resources, causing a lot of variation in the results.
How can I easily set up a quiet system that has a minimum of other processes running in the background? Obviously I can avoid opening Firefox, playing Spotify in the background, but even without opening any other processes besides Terminal, there are many things using CPU on a typical Ubuntu system.
I'm willing to reboot to access this quiet configuration if need be.
