sched: fix the inaccurate cpuload statistics issue

Non-fixed clock source will lead to inaccurate cpuload statistics

before:
5     5 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%   2.5% cpuload -p 50
6     6 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%   0.7% cpuload -p 10
7     7 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%   2.2% cpuload -p 20
after:
5     5 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%  50.8% cpuload -p 50
6     6 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%  10.8% cpuload -p 10
7     7 253 RR       Task      - Waiting  Signal    0000000000000000 0002000 0000624  31.2%  20.0% cpuload -p 20
Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>

sched/Kconfig

@@ -1027,7 +1027,6 @@ config SCHED_CPULOAD_NONE
 
 config SCHED_CPULOAD_SYSCLK
 	bool "Use system clock"
-	depends on !SCHED_TICKLESS
 	---help---
 		If this option is enabled, the system clock is used for cpu load
 		measurement by default.
@@ -1077,19 +1076,18 @@ config SCHED_CPULOAD_CRITMONITOR
 
 endchoice
 
-if SCHED_CPULOAD_EXTCLK
-
 config SCHED_CPULOAD_TICKSPERSEC
-	int "External clock rate"
+	int "CPU load sampling clock frequency(HZ)"
 	default 100
 	---help---
-		If an external clock is used to drive the sampling for the CPU load
-		calculations, then this value must be provided.  This value provides
-		the rate of the external clock interrupts in units of ticks per
-		second.  The default value of 100 corresponds to a 100Hz clock.  NOTE:
+		CPU load sampling clock frequency, in HZ. Use sysclk clock source,
+		use wdt, EXTCLK clock source, use an external timer.
+		The default value of 100 corresponds to a 100Hz clock.  NOTE:
 		that 100Hz is the default frequency of the system time and, hence,
 		the worst possible choice in most cases.
 
+if SCHED_CPULOAD_EXTCLK
+
 choice
 	prompt "Select CPU load timer"
 	default CPULOAD_ONESHOT

sched/clock/clock.h

@@ -87,4 +87,8 @@ void clock_timer(void);
 
 void perf_init(void);
 
+#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
+void cpuload_init(void);
+#endif
+
 #endif /* __SCHED_CLOCK_CLOCK_H */

sched/clock/clock_initialize.c

@@ -231,6 +231,10 @@ void clock_initialize(void)
 
   perf_init();
 
+#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
+  cpuload_init();
+#endif
+
   sched_trace_end();
 }
 

sched/sched/sched_cpuload.c

@@ -31,6 +31,7 @@
 
 #include <nuttx/clock.h>
 #include <nuttx/irq.h>
+#include <nuttx/wdog.h>
 
 #include "sched/sched.h"
 
@@ -61,6 +62,11 @@
       CONFIG_SCHED_CPULOAD_TIMECONSTANT * \
       CPULOAD_TICKSPERSEC)
 
+/* The sampling period in system timer ticks */
+
+#define CPULOAD_SAMPLING_PERIOD \
+     (TICK_PER_SEC / CONFIG_SCHED_CPULOAD_TICKSPERSEC)
+
 /****************************************************************************
  * Public Data
  ****************************************************************************/
@@ -80,6 +86,34 @@
 
 volatile clock_t g_cpuload_total;
 
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: cpuload_callback
+ *
+ * Description:
+ *   This is the callback function that will be invoked when the watchdog
+ *   timer expires.
+ *
+ * Input Parameters:
+ *   argc - the argument passed with the timer when the timer was started.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
+static void cpuload_callback(wdparm_t arg)
+{
+  FAR struct wdog_s *wdog = (FAR struct wdog_s *)arg;
+  nxsched_process_cpuload_ticks(CPULOAD_SAMPLING_PERIOD);
+  wd_start(wdog, CPULOAD_SAMPLING_PERIOD, cpuload_callback, arg);
+}
+#endif
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -221,3 +255,26 @@ int clock_cpuload(int pid, FAR struct cpuload_s *cpuload)
   leave_critical_section(flags);
   return ret;
 }
+
+/****************************************************************************
+ * Name: cpuload_init
+ *
+ * Description:
+ *   Initialize the CPU load measurement logic.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
+void cpuload_init(void)
+{
+  static struct wdog_s g_cpuload_wdog;
+  wd_start(&g_cpuload_wdog, CPULOAD_SAMPLING_PERIOD, cpuload_callback,
+           (wdparm_t)&g_cpuload_wdog);
+}
+#endif

sched/sched/sched_processtimer.c

@@ -182,14 +182,6 @@ void nxsched_process_timer(void)
 
   clock_timer();
 
-#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
-  /* Perform CPU load measurements (before any timer-initiated context
-   * switches can occur)
-   */
-
-  nxsched_process_cpuload();
-#endif
-
   /* Check if the currently executing task has exceeded its
    * timeslice.
    */

sched/sched/sched_timerexpiration.c

@@ -339,14 +339,6 @@ static clock_t nxsched_timer_process(clock_t ticks, clock_t elapsed,
   clock_update_wall_time();
 #endif
 
-#ifdef CONFIG_SCHED_CPULOAD_SYSCLK
-  /* Perform CPU load measurements (before any timer-initiated context
-   * switches can occur)
-   */
-
-  nxsched_process_cpuload_ticks(elapsed);
-#endif
-
   /* Check for operations specific to scheduling policy of the currently
    * active task.
    */