Em Mon, Apr 16, 2018 at 10:04:53PM +0000, Stephane Eranian escreveu: > Hi, > > I am trying to understand what the exclude_idle event attribute is supposed > to accomplish. > As per the definition in the header file: > > exclude_idle : 1, /* don't count when idle */ > > Naively, I thought it would simply stop the event when running in the > context of the idle task (swapper, pid 0) on any CPU. That would seem to > match the succinct description. > > However, running a simple: > > $ perf record -a -e cycles:I sleep 5 > perf_event_attr: > sample_type IP|TID|TIME|CPU|PERIOD > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID > exclude_idle 1 > > on an idle machine, showed me that this is not what is actually happening: > $ perf script > swapper 0 [000] 1132634.287442: 1 cycles:I: > ffffffff8100b1fb __intel_pmu_enable_all.isra.17 ([kernel.kallsyms]) > swapper 0 [001] 1132634.287498: 1 cycles:I: > ffffffff8100b1fb __intel_pmu_enable_all.isra.17 ([kernel.kallsyms]) > > > After looking at the code, it all made sense, it seems to current > implementation is only relevant for sw events. I don't understand why. > > I am left wondering what is the goal of exclude_idle?
To do something it is not doing, i.e. to do what you expected it to do. There were messages exchanged recently where PeterZ said that this is just that needs fixing. - Arnaldo
