From: Yonghong Song <y...@fb.com> Date: Thu, 5 Oct 2017 09:19:18 -0700
> Hardware pmu counters are limited resources. When there are more > pmu based perf events opened than available counters, kernel will > multiplex these events so each event gets certain percentage > (but not 100%) of the pmu time. In case that multiplexing happens, > the number of samples or counter value will not reflect the > case compared to no multiplexing. This makes comparison between > different runs difficult. > > Typically, the number of samples or counter value should be > normalized before comparing to other experiments. The typical > normalization is done like: > normalized_num_samples = num_samples * time_enabled / time_running > normalized_counter_value = counter_value * time_enabled / time_running > where time_enabled is the time enabled for event and time_running is > the time running for event since last normalization. > > This patch set implements two helper functions. > The helper bpf_perf_event_read_value reads counter/time_enabled/time_running > for perf event array map. The helper bpf_perf_prog_read_value read > counter/time_enabled/time_running for bpf prog with type > BPF_PROG_TYPE_PERF_EVENT. Series applied to net-next, thanks.
