Add cpu load (#14)

.github/memsize.baseline

@@ -1,2 +1,2 @@
    text	   data	    bss	    dec	    hex	filename
- 181721	  51664	 371173	 604558	  9398e	build/template.elf
+ 182109	  51744	 371125	 604978	  93b32	build/template.elf

ports/esp-idf/build.cmake

@@ -61,12 +61,14 @@ add_executable(${PROJECT_EXECUTABLE}
 	${LIBMCU_ROOT}/ports/posix/button.c
 )
 
+idf_build_set_property(COMPILE_DEFINITIONS -DtraceTASK_SWITCHED_IN=on_task_switch_in APPEND)
+idf_build_set_property(COMPILE_DEFINITIONS -DxPortIsInsideInterrupt=xPortInIsrContext APPEND)
+idf_build_set_property(C_COMPILE_OPTIONS "-Wno-implicit-function-declaration" APPEND)
+
 target_compile_definitions(${PROJECT_EXECUTABLE}
 	PRIVATE
 		${APP_DEFS}
-
-		ESP_PLATFORM=1
-		xPortIsInsideInterrupt=xPortInIsrContext
+		ESP_PLATFORM
 )
 target_include_directories(${PROJECT_EXECUTABLE}
 	PRIVATE

ports/esp-idf/cpuload.c

@@ -0,0 +1,69 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Kyunghwan Kwon <k@libmcu.org>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "libmcu/board.h"
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+
+#define CPULOAD_CALC_INTERVAL_MS	1000
+
+static struct cpuload {
+	uint32_t idle_time_elapsed;
+	uint32_t running_time_elapsed;
+	TaskHandle_t prev_task;
+	uint8_t cpuload;
+} cores[SOC_CPU_CORES_NUM];
+
+void on_task_switch_in(void)
+{
+	static uint32_t t0;
+	static uint32_t sum_elapsed;
+
+	uint32_t t1 = board_get_time_since_boot_ms();
+	uint32_t elapsed = t1 - t0;
+
+	/* NOTE: count at least 1 even if the task has run for much shorter time
+	 * as millisecond unit timer used here. For fine granularity, introduce
+	 * high-resolution timer. */
+	if (elapsed == 0) {
+		elapsed = 1;
+	}
+
+	TaskHandle_t current = xTaskGetCurrentTaskHandle();
+	struct cpuload *core = &cores[xPortGetCoreID()];
+
+	if (current == xTaskGetIdleTaskHandle()) {
+		if (current == core->prev_task) { /* idle to idle */
+			core->idle_time_elapsed += elapsed;
+		} else { /* active to idle */
+			core->running_time_elapsed += elapsed;
+		}
+	} else {
+		if (current == core->prev_task) { /* active to active */
+			core->running_time_elapsed += elapsed;
+		} else { /* idle to active */
+			core->idle_time_elapsed += elapsed;
+		}
+	}
+
+	sum_elapsed += elapsed;
+	core->cpuload = (uint8_t)(core->running_time_elapsed * 100 /
+			(core->running_time_elapsed + core->idle_time_elapsed));
+
+	if (sum_elapsed >= CPULOAD_CALC_INTERVAL_MS) {
+		core->running_time_elapsed = core->idle_time_elapsed = 0;
+		sum_elapsed = 0;
+	}
+
+	t0 = t1;
+	core->prev_task = current;
+}
+
+uint8_t board_cpuload(int core_id)
+{
+	return cores[core_id].cpuload;
+}