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/************************************************************************
* sched/sched_cpuload.c
*
* Copyright (C) 2014 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
************************************************************************/
/************************************************************************
* Included Files
************************************************************************/
#include <nuttx/config.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/clock.h>
#include <arch/irq.h>
#include "os_internal.h"
#ifdef CONFIG_SCHED_CPULOAD
/************************************************************************
* Pre-processor Definitions
************************************************************************/
/* Are we using the system timer, or an external clock? Get the rate
* of the sampling in ticks per second for the selected timer.
*/
#ifdef CONFIG_SCHED_CPULOAD_EXTCLK
# ifndef CONFIG_SCHED_CPULOAD_TICKSPERSEC
# error CONFIG_SCHED_CPULOAD_TICKSPERSEC is not defined
# endif
# define CPULOAD_TICKSPERSEC CONFIG_SCHED_CPULOAD_TICKSPERSEC
#else
# define CPULOAD_TICKSPERSEC CLOCKS_PER_SEC
#endif
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Public Variables
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/* This is the total number of clock tick counts. Essentially the
* 'denominator' for all CPU load calculations.
*/
volatile uint32_t g_cpuload_total;
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: sched_process_cpuload
*
* Description:
* Collect data that can be used for CPU load measurements.
*
* Inputs:
* None
*
* Return Value:
* None
*
* Assumptions/Limitations:
* This function is called from a timer interrupt handler with all
* interrupts disabled.
*
************************************************************************/
void weak_function sched_process_cpuload(void)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
int hash_index;
int i;
/* Increment the count on the currently executing thread
*
* NOTE also that CPU load measurement data is retained in the g_pidhash
* table vs. in the TCB which would seem to be the more logic place. It
* is place in the hash table, instead, to facilitate CPU load adjustments
* on all threads during timer interrupt handling. sched_foreach() could
* do this too, but this would require a little more overhead.
*/
hash_index = PIDHASH(rtcb->pid);
g_pidhash[hash_index].ticks++;
/* Increment tick count. If the accumulated tick value exceed a time
* constant, then shift the accumulators.
*/
if (++g_cpuload_total > (CONFIG_SCHED_CPULOAD_TIMECONSTANT * CPULOAD_TICKSPERSEC))
{
uint32_t total = 0;
/* Divide the tick count for every task by two and recalculate the
* total.
*/
for (i = 0; i < CONFIG_MAX_TASKS; i++)
{
g_pidhash[i].ticks >>= 1;
total += g_pidhash[i].ticks;
}
/* Save the new total. */
g_cpuload_total = total;
}
}
/****************************************************************************
* Function: clock_cpuload
*
* Description:
* Return load measurement data for the select PID.
*
* Parameters:
* pid - The task ID of the thread of interest. pid == 0 is the IDLE thread.
* cpuload - The location to return the CPU load
*
* Return Value:
* OK (0) on success; a negated errno value on failure. The only reason
* that this function can fail is if 'pid' no longer refers to a valid
* thread.
*
* Assumptions:
*
****************************************************************************/
int clock_cpuload(int pid, FAR struct cpuload_s *cpuload)
{
irqstate_t flags;
int hash_index = PIDHASH(pid);
int ret = -ESRCH;
DEBUGASSERT(cpuload);
/* Momentarily disable interrupts. We need (1) the task to stay valid
* while we are doing these operations and (2) the tick counts to be
* synchronized when read.
*/
flags = irqsave();
/* Make sure that the entry is valid (TCB field is not NULL) and matches
* the requested PID. The first check is needed if the thread has exited.
* The second check is needed for the case where the task associated with
* the requested PID has exited and the slot has been taken by another
* thread with a different PID.
*
* NOTE also that CPU load measurement data is retained in the g_pidhash
* table vs. in the TCB which would seem to be the more logic place. It
* is place in the hash table, instead, to facilitate CPU load adjustments
* on all threads during timer interrupt handling. sched_foreach() could
* do this too, but this would require a little more overhead.
*/
if (g_pidhash[hash_index].tcb && g_pidhash[hash_index].pid == pid)
{
cpuload->total = g_cpuload_total;
cpuload->active = g_pidhash[hash_index].ticks;
ret = OK;
}
irqrestore(flags);
return ret;
}
#endif /* CONFIG_SCHED_CPULOAD */
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