Linux Perf

Take a note of linux perf tool, more details will be added.

usermode part

tools/perf/builtin-record.c

\-- cmd_record
|   \-- __cmd_record
|   |  \-- record__open
|   |  |   \-- evsel__open

tools/perf/util/evsel.c

\-- evsel__open
|   \-- evsel__open_cpu
|   |   \-- sys_perf_event_open

kernelmode part

kernel/events/core.c

\-- sys_perf_event_open
|   \-- perf_event_alloc
|   |   \-- perf_init_event
|   |   |   \-- perf_try_init_event
|   |   |   |   \-- pmu->event_init

pmu register

kernel/events/core.c

perf_pmu_register(&perf_swevent, "software", PERF_TYPE_SOFTWARE);
perf_pmu_register(&perf_cpu_clock, NULL, -1);
perf_pmu_register(&perf_task_clock, NULL, -1);
perf_tp_register();

static inline void perf_tp_register(void)
{
	perf_pmu_register(&perf_tracepoint, "tracepoint", PERF_TYPE_TRACEPOINT);
#ifdef CONFIG_KPROBE_EVENTS
	perf_pmu_register(&perf_kprobe, "kprobe", -1);
#endif
#ifdef CONFIG_UPROBE_EVENTS
	perf_pmu_register(&perf_uprobe, "uprobe", -1);
#endif
}

take tracepoint as example

kernel/events/core.c

static struct pmu perf_tracepoint = {
	.task_ctx_nr	= perf_sw_context,

	.event_init	= perf_tp_event_init,
	.add		= perf_trace_add,
	.del		= perf_trace_del,
	.start		= perf_swevent_start,
	.stop		= perf_swevent_stop,
	.read		= perf_swevent_read,
};

\-- pmu->event_init
|   \-- perf_tp_event_init
|   |   \-- perf_trace_init

kernel/trace/trace_event_perf.c

\-- perf_trace_init
|   \-- perf_trace_event_init
|   |   \-- perf_trace_event_reg
|   |   |   \-- tp_event->class->reg

tp_event is a trace_event_call structure which is defined when we use the very complicated macro TRACE_EVENT for specific tracepoint, all trace_event_call structures will be linked to a global list ftrace_events.

for tracepoint, the tp_event->class->reg will be trace_event_reg, it will register the perf_event callback perf_trace_##call to the specific tracepoint, the callback perf_trace_##call which is also define by the very complicated macro TRACE_EVENT, will write collected data to the ring buffer

Written on July 10, 2022