I have seen this term in several posts about profiling applications but I don't understand what it actually means and how it affects profiling results.
I have seen it here for dtrace:
The rate is also increased to 199 Hertz, as capturing kernel stacks is much less expensive than user-level stacks. The odd numbered rates, 99 and 199, are used to avoid sampling in lockstep with other activity and producing misleading results.
-F 99: sample at 99 Hertz (samples per second). I'll sometimes sample faster than this (up to 999 Hertz), but that also costs overhead. 99 Hertz should be negligible. Also, the value '99' and not '100' is to avoid lockstep sampling, which can produce skewed results.
From what I have seen all profilers should avoid lockstep sampling because results can be "skewed" and "misleading" but I don't understand why. I guess that this question is applicable to all profilers but I am interested in perf on linux.