u/live_stats: Add helper to do live statistics on nano-seconds durations

src/xrt/auxiliary/util/CMakeLists.txt

@@ -61,6 +61,8 @@ add_library(
 	u_json.hpp
 	u_limited_unique_id.cpp
 	u_limited_unique_id.h
+	u_live_stats.cpp
+	u_live_stats.h
 	u_logging.c
 	u_logging.h
 	u_metrics.c

src/xrt/auxiliary/util/u_live_stats.cpp

@@ -0,0 +1,117 @@
+// Copyright 2024, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Live stats tracking and printing.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @ingroup aux_util
+ */
+
+#include "u_live_stats.h"
+
+#include <inttypes.h>
+#include <algorithm>
+
+
+/*
+ *
+ * Helper functions.
+ *
+ */
+
+static void
+print_as_ms(u_pp_delegate_t dg, uint64_t value_ns)
+{
+	uint64_t in_us = value_ns / 1000;
+	uint64_t in_ms = in_us / 1000;
+	uint64_t in_1_000_ms = in_ms / 1000;
+	uint64_t in_1_000_000_ms = in_1_000_ms / 1000;
+
+	// Prints " M'TTT'###.FFFms"
+
+	// " M'"
+	if (in_1_000_000_ms >= 1) {
+		u_pp(dg, " %" PRIu64 "'", in_1_000_000_ms);
+	} else {
+		//       " M'"
+		u_pp(dg, "   ");
+	}
+
+	// "TTT'"
+	if (in_1_000_ms >= 1000) {
+		// Need to pad with zeros
+		u_pp(dg, "%03" PRIu64 "'", in_1_000_ms % 1000);
+	} else if (in_1_000_ms >= 1) {
+		// Pad with spaces, we need to write a number.
+		u_pp(dg, "%3" PRIu64 "'", in_1_000_ms);
+	} else {
+		//       "TTT'"
+		u_pp(dg, "    ");
+	}
+
+	// "###"
+	if (in_ms >= 1000) {
+		// Need to pad with zeros
+		u_pp(dg, "%03" PRIu64, in_ms % 1000);
+	} else {
+		// Pad with spaces, always need a numbere here.
+		u_pp(dg, "%3" PRIu64, in_ms % 1000);
+	}
+
+	// ".FFFms"
+	u_pp(dg, ".%03" PRIu64 "ms", in_us % 1000);
+}
+
+
+/*
+ *
+ * 'Exported' functions.
+ *
+ */
+
+extern "C" void
+u_ls_ns_get_and_reset(struct u_live_stats_ns *uls, uint64_t *out_median, uint64_t *out_mean, uint64_t *out_worst)
+{
+	uint32_t count = uls->value_count;
+
+	if (count == 0) {
+		*out_median = 0;
+		*out_mean = 0;
+		*out_worst = 0;
+		return;
+	}
+
+	std::sort(&uls->values[0], &uls->values[count]);
+
+	uint64_t worst = uls->values[count - 1]; // Always greater then 0.
+	uint64_t median = uls->values[count / 2];
+
+	uint64_t mean = 0;
+	for (uint32_t i = 0; i < count; ++i) {
+		mean += uls->values[i] / count;
+	}
+
+	uls->value_count = 0;
+	*out_median = median;
+	*out_mean = mean;
+	*out_worst = worst;
+}
+
+extern "C" void
+u_ls_ns_print_header(u_pp_delegate_t dg)
+{
+	//       "xxxxYYYYzzzzWWWW M'TTT'###.FFFms M'TTT'###.FFFms M'TTT'###.FFFms"
+	u_pp(dg, "            name          median            mean           worst");
+}
+
+extern "C" void
+u_ls_ns_print_and_reset(struct u_live_stats_ns *uls, u_pp_delegate_t dg)
+{
+	uint64_t median, mean, worst;
+	u_ls_ns_get_and_reset(uls, &median, &mean, &worst);
+
+	u_pp(dg, "%16s", uls->name);
+	print_as_ms(dg, median);
+	print_as_ms(dg, mean);
+	print_as_ms(dg, worst);
+}

src/xrt/auxiliary/util/u_live_stats.h

@@ -0,0 +1,106 @@
+// Copyright 2024, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Live stats tracking and printing.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @ingroup aux_util
+ */
+#pragma once
+
+#include "xrt/xrt_compiler.h"
+
+#include "util/u_pretty_print.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*!
+ * Number of chars for the name of the live stats.
+ *
+ * @ingroup aux_util
+ */
+#define U_LIVE_STATS_NAME_COUNT (16)
+
+/*!
+ * Max number of values that can be put into the trackers.
+ *
+ * @ingroup aux_util
+ */
+#define U_LIVE_STATS_VALUE_COUNT (1024)
+
+/*!
+ * Struct to do live statistic tracking and printing of nano-seconds values,
+ * used by amongst other the compositor pacing code.
+ *
+ * @ingroup aux_util
+ */
+struct u_live_stats_ns
+{
+	//! Small name used for printing.
+	char name[U_LIVE_STATS_NAME_COUNT];
+
+	//! Number of values currently in struct.
+	uint32_t value_count;
+
+	//! The values that will be used to calculate statistics.
+	uint64_t values[U_LIVE_STATS_VALUE_COUNT];
+};
+
+/*!
+ * Add a value to the live stats struct, returns true if the struct is full
+ * either before or after adding the value.
+ *
+ * @public @memberof u_live_stats_ns
+ * @ingroup aux_util
+ */
+static inline bool
+u_ls_ns_add(struct u_live_stats_ns *uls, uint64_t value)
+{
+	if (uls->value_count >= ARRAY_SIZE(uls->values)) {
+		return true;
+	}
+
+	uls->values[uls->value_count++] = value;
+
+	if (uls->value_count >= ARRAY_SIZE(uls->values)) {
+		return true;
+	}
+
+	return false;
+}
+
+/*!
+ * Get the median, mean and worst of the current set of values,
+ * then reset the struct.
+ *
+ * @public @memberof u_live_stats_ns
+ */
+void
+u_ls_ns_get_and_reset(struct u_live_stats_ns *uls, uint64_t *out_median, uint64_t *out_mean, uint64_t *out_worst);
+
+/*!
+ * Prints a header that looks nice before @ref u_ls_print_and_reset,
+ * adding details about columns. Doesn't include any newlines.
+ *
+ * @public @memberof u_live_stats_ns
+ */
+void
+u_ls_ns_print_header(u_pp_delegate_t dg);
+
+/*!
+ * Prints the calculated values and resets the struct, can be used with
+ * @ref u_ls_ns_print_header to get a nice header to the values. Doesn't
+ * include any newlines.
+ *
+ * @public @memberof u_live_stats_ns
+ */
+void
+u_ls_ns_print_and_reset(struct u_live_stats_ns *uls, u_pp_delegate_t dg);
+
+
+#ifdef __cplusplus
+}
+#endif