Do you mean SMT (e.g. HyperThreding in Intel)? If you mean CPUs in the same socket, core_siblings_list can be used (but stopping sibling SMT threads is more important.)
Maybe it is nice to mention about numactl command in case for benchmarking parallel programs.
Simple explanation on the meaning or -r option will be valuable, i.e. -r 10 will increase the execution time 10x.
Should we have a "General" section with this note? Certainly this is true for FreeBSD as well, but it seems like it will apply everywhere.
The advice could also be in a general section, with just the specific commands specific to the OS perhaps. For example, the tmpfs explanation also applies to FreeBSD, and even on other operating systems the general advice is sound. (Actually, the command is also identical on FreeBSD for tmpfs, but probably not elsewhere.)
I think that at the moment, these are mainly tips specifically for how to set up a system to reduce noisiness in benchmark results.
nitpick: s/to be in control of all the possible sources of noise/reduce all possible sources of noise as much as possible/?
At http://lnt.llvm.org/quickstart.html#running-tests, there are a few hints under number 3 on how to reduce noise and cope with the remaining noise better when you use LNT for benchmarking. Would it be useful to have a pointer here to there?
Results will be less noisy with address space randomization turned off, but I continue to think that incorrectly skews experiment results.