path: root/arch/x86/net
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authorLeo Yan <leo.yan@linaro.org>2018-02-26 09:19:12 +0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-02-26 10:54:02 +0100
commitc53507778998d45543b27266742d04cd384de356 (patch)
tree78eb11248397edee9dc93997838e2d2a8ebeb01b /arch/x86/net
parent7d72637eb39f8336d8a07f1583fcc1dffce413e5 (diff)
samples/bpf: Add program for CPU state statistics
CPU is active when have running tasks on it and CPUFreq governor can select different operating points (OPP) according to different workload; we use 'pstate' to present CPU state which have running tasks with one specific OPP. On the other hand, CPU is idle which only idle task on it, CPUIdle governor can select one specific idle state to power off hardware logics; we use 'cstate' to present CPU idle state. Based on trace events 'cpu_idle' and 'cpu_frequency' we can accomplish the duration statistics for every state. Every time when CPU enters into or exits from idle states, the trace event 'cpu_idle' is recorded; trace event 'cpu_frequency' records the event for CPU OPP changing, so it's easily to know how long time the CPU stays in the specified OPP, and the CPU must be not in any idle state. This patch is to utilize the mentioned trace events for pstate and cstate statistics. To achieve more accurate profiling data, the program uses below sequence to insure CPU running/idle time aren't missed: - Before profiling the user space program wakes up all CPUs for once, so can avoid to missing account time for CPU staying in idle state for long time; the program forces to set 'scaling_max_freq' to lowest frequency and then restore 'scaling_max_freq' to highest frequency, this can ensure the frequency to be set to lowest frequency and later after start to run workload the frequency can be easily to be changed to higher frequency; - User space program reads map data and update statistics for every 5s, so this is same with other sample bpf programs for avoiding big overload introduced by bpf program self; - When send signal to terminate program, the signal handler wakes up all CPUs, set lowest frequency and restore highest frequency to 'scaling_max_freq'; this is exactly same with the first step so avoid to missing account CPU pstate and cstate time during last stage. Finally it reports the latest statistics. The program has been tested on Hikey board with octa CA53 CPUs, below is one example for statistics result, the format mainly follows up Jesper Dangaard Brouer suggestion. Jesper reminds to 'get printf to pretty print with thousands separators use %' and setlocale(LC_NUMERIC, "en_US")', tried three different arm64 GCC toolchains (5.4.0 20160609, 6.2.1 20161016, 6.3.0 20170516) but all of them cannot support printf flag character %' on arm64 platform, so go back print number without grouping mode. CPU states statistics: state(ms) cstate-0 cstate-1 cstate-2 pstate-0 pstate-1 pstate-2 pstate-3 pstate-4 CPU-0 767 6111 111863 561 31 756 853 190 CPU-1 241 10606 107956 484 125 646 990 85 CPU-2 413 19721 98735 636 84 696 757 89 CPU-3 84 11711 79989 17516 909 4811 5773 341 CPU-4 152 19610 98229 444 53 649 708 1283 CPU-5 185 8781 108697 666 91 671 677 1365 CPU-6 157 21964 95825 581 67 566 684 1284 CPU-7 125 15238 102704 398 20 665 786 1197 Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Leo Yan <leo.yan@linaro.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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