//kernel/timer.c1254 active_tasks = count_active_tasks();1256 CALC_LOAD(avenrun[0], EXP_1, active_tasks);1257 CALC_LOAD(avenrun[1], EXP_5, active_tasks);1258 CALC_LOAD(avenrun[2], EXP_15, active_tasks);//include/linux/sched.h110 #define FSHIFT 11 /* nr of bits of PRecision */111 #define FIXED_1 (1<112 #define LOAD_FREQ (5*HZ) /* 5 sec intervals */113 #define EXP_1 1884 /* 1/exp(5sec/1min) as fixed-point */114 #define EXP_5 2014 /* 1/exp(5sec/5min) */115 #define EXP_15 2037 /* 1/exp(5sec/15min) */117 #define CALC_LOAD(load,exp,n) /118 load *= exp; /119 load += n*(FIXED_1-exp); /120 load >>= FSHIFT; load(t) = ( load(t-1)*exp(i) + n(t)*(2048-exp(i)) ) / 2048 load(t-1)为上次计算出的结果 n(t)为t时刻的活动进程数 计算方式是累加各个CPU的运行队列中running和uninterruptible的值 再乘以2048 计算方式如下：1946 unsigned long nr_active(void)1947 {1948 unsigned long i, running = 0, uninterruptible = 0;19491950 for_each_online_cpu(i) {1951 running += cpu_rq(i)->nr_running;1952 uninterruptible += cpu_rq(i)->nr_uninterruptible;1953 }19541955 if (unlikely((long)uninterruptible < 0))1956 uninterruptible = 0;19571958 return running + uninterruptible;1959 }1226 static unsigned long count_active_tasks(void)1227 {1228 return nr_active() * FIXED_1;1229 } exp(1) = 1884 exp(5) = 2014 exp(15) = 2037 exp(i) = 2048 * e^(-1/12/i) |
