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cpu 占用率之 wa

wa 占用率为100%时，并不是 cpu 在忙转，此时cpu 一直执行idle 进程。 

void __sched io_schedule(void)

{ struct rq *rq = raw_rq(); delayacct_blkio_start(); atomic_inc(&rq->nr_iowait); current->in_iowait = 1; schedule(); current->in_iowait = 0; atomic_dec(&rq->nr_iowait); delayacct_blkio_end(); }

update_process_times->account_process_tick

void account_process_tick(struct task_struct *p, int user_tick)

{ cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy); struct rq *rq = this_rq(); if (user_tick) account_user_time(p, cputime_one_jiffy, one_jiffy_scaled); else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET)) account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,    one_jiffy_scaled); else account_idle_time(cputime_one_jiffy); }

void account_idle_time(cputime_t cputime)

{ struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat; cputime64_t cputime64 = cputime_to_cputime64(cputime); struct rq *rq = this_rq(); if (atomic_read(&rq->nr_iowait) > 0) cpustat->iowait = cputime64_add(cpustat->iowait, cputime64); else cpustat->idle = cputime64_add(cpustat->idle, cputime64); }

s3c2410_timer_interrupt ->timer_tick ->

void timer_tick(void)

{ profile_tick(CPU_PROFILING); do_leds(); do_set_rtc(); write_seqlock(&xtime_lock); do_timer(1); write_sequnlock(&xtime_lock); #ifndef CONFIG_SMP update_process_times(user_mode(get_irq_regs())); #endif }

void do_timer(unsigned long ticks)

{ jiffies_64 += ticks; update_wall_time(); calc_global_load(); }

cpu 占用率之 ni :

tmp = cputime_to_cputime64(cputime);

if (TASK_NICE(p) > 0) cpustat->nice = cputime64_add(cpustat->nice, tmp); else cpustat->user = cputime64_add(cpustat->user, tmp);

/*

 * Convert user-nice values [ -20 ... 0 ... 19 ]  * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],  * and back.  */ #define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20) #define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20) #define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)

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