On Wed, 2 Sep 2015, David Ahern wrote: > The counter values are not relevant for profiling. They are programmed to > rollover and generate an NMI which causes the sample to be taken.
They might not be relevant for profiling, but some people use the perf counters for other tasks. For example, when measuring phase plot behavior for a system, it would be great if you'd be able to say I want a snapshot sample of the cycle and instruction counters every 10ms, and then you can plot the CPI behavior of the system. as far as I can tell you can't really do this with perf (the -I option only lets you get down to 100ms). I ended up trying to write a custom program to do this, but it turns out the perf sampling interface has really high overhead when doing this, and the interrupt throttle kicks in which makes it useless. It's a shame, as the old "pfmon" tool that came with perfmon2 could do this kind of measurement very easily. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
