> > [email protected] writes: > > > From: Kan Liang <[email protected]> > > > > The rough overhead rate can be caculated by the sum of all kinds of > > overhead / elapsed time. > > If the overhead rate is higher than 10%, warning the user. > > Thinking about this more: this is comparing the cost of a single CPU to the > total wall clock time. This isn't very good and can give confusing results > with > many cores. > > Perhaps we need two separate metrics here: > > - cost of perf record on its CPU (or later on if it gets multi threaded > more multiple). Warn if this is >50% or so.
What's the formula for cost of perf record on its CPU? The cost only includes user space overhead or all overhead? What is the divisor? > - average perf collection overhead on a CPU. The 10% threshold here > seems appropiate. For the average, do you mean add all overheads among CPUs together and divide the CPU#? To calculate the rate, the divisor is wall clock time, right? Thanks, Kan
