Spike profiler

profiling.cpp

@@ -0,0 +1,130 @@
+#ifdef PROFILING
+
+#include "profiling.h"
+
+#include "str_util.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+
+struct Event
+{
+	const char *name;
+	uint32_t begin_idx;
+	struct timespec ts;
+};
+
+static constexpr int MAX_EVENTS = 512; // must be pow2
+static Event s_events[MAX_EVENTS]; // circular buffer
+static uint32_t s_event_tail = 0;
+
+static constexpr Event *get_event(uint32_t idx)
+{
+	return &s_events[idx % MAX_EVENTS];
+}
+
+uint32_t profiling_event_begin(const char *name)
+{
+	Event *newEvent = get_event(s_event_tail);
+	newEvent->begin_idx = s_event_tail;
+	newEvent->name = name;
+	clock_gettime(CLOCK_MONOTONIC, &newEvent->ts);
+
+	uint32_t r = s_event_tail;
+	s_event_tail++;
+	return r;
+}
+
+void profiling_event_end(uint32_t begin_idx, const char *name)
+{
+	Event *newEvent = get_event(s_event_tail);
+	newEvent->begin_idx = begin_idx;
+	newEvent->name = name;
+	clock_gettime(CLOCK_MONOTONIC, &newEvent->ts);
+	s_event_tail++;
+}
+
+// result_ns = a - b
+static uint64_t delta_ns(const struct timespec *a, const struct timespec *b)
+{
+	struct timespec ts;
+
+	ts.tv_sec = a->tv_sec - b->tv_sec;
+	ts.tv_nsec = a->tv_nsec - b->tv_nsec;
+	if (ts.tv_nsec < 0)
+	{
+		ts.tv_nsec += 1000000000;
+		ts.tv_sec -= 1;
+	}
+
+	uint64_t delta = ts.tv_sec * 1000000000ULL;
+	delta += ts.tv_nsec;
+	return delta;
+}
+
+
+// Bookkeeping data for spike report
+static uint64_t inclusive_times[MAX_EVENTS];
+static uint64_t other_times[MAX_EVENTS];
+static uint32_t pair_stack[MAX_EVENTS / 2];
+
+void profiling_spike_report(uint32_t begin_idx, uint32_t spike_us)
+{
+	int stack_pos = 0;
+
+	if ((s_event_tail - begin_idx) < 2) return; // not enough events
+	if ((s_event_tail - begin_idx) > MAX_EVENTS) return; // too many events
+
+	const uint64_t total_ns = delta_ns(&get_event(s_event_tail - 1)->ts, &get_event(begin_idx)->ts);
+
+	if (total_ns < (spike_us * 1000ULL)) return; // below threshold
+
+	for (uint32_t idx = begin_idx; idx != s_event_tail; idx++)
+	{
+		const uint32_t cyc_idx = idx % MAX_EVENTS;
+		Event *event = get_event(idx);
+
+		if (event->begin_idx == idx)
+		{
+			pair_stack[stack_pos] = cyc_idx;
+			inclusive_times[cyc_idx] = 0;
+			other_times[cyc_idx] = 0;
+			stack_pos++;
+		}
+		else
+		{
+			stack_pos--;
+			uint32_t span_idx = pair_stack[stack_pos];
+			const uint64_t inclusive_ns = delta_ns(&event->ts, &get_event(span_idx)->ts);
+			inclusive_times[span_idx] = inclusive_ns;
+			if (stack_pos > 0) other_times[pair_stack[stack_pos-1]] += inclusive_ns;
+		}
+	}
+
+	char label[256];
+	int indent = 0;
+	printf("\n%lluus spike over %uus limit.\n", total_ns / 1000ULL, spike_us);
+	printf("+----- Name -----------------------------------------+ Inc(us) + Exc(us) +\n");
+	for (uint32_t idx = begin_idx; idx != s_event_tail; idx++)
+	{
+		const uint32_t cyc_idx = idx % MAX_EVENTS;
+		Event *event = get_event(idx);
+
+		if (event->begin_idx == idx)
+		{
+			memset(label, ' ', indent);
+			strcpyz(label + indent, sizeof(label) - indent, event->name);
+			printf("| %-50s | %7llu | %7llu |\n", label, inclusive_times[cyc_idx] / 1000ULL, (inclusive_times[cyc_idx] - other_times[cyc_idx]) / 1000ULL);
+			indent += 2;
+		}
+		else
+		{
+			indent -= 2;
+		}
+	}
+	printf("+----------------------------------------------------+---------+---------+\n\n");
+	fflush(stdout);
+}
+
+#endif // PROFILING