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内核可以灵活配置HZ为100、250或者1000。而时钟中断触发的频度为HZ。
两者是如何关联的呢？以X86传统的PIT为例。
先看一下初始化。static void init_pit_timer(enum clock_event_mode mode, struct clock_event_device *evt) switch (mode) case CLOCK_EVT_MODE_PERIODIC: /* binary, mode 2, LSB/MSB, ch 0 */ outb_pit(0x34, PIT_MODE); outb_pit(LATCH & 0xff , PIT_CH0); /* LSB */ /* LATCH is used in the interval timer and ftape setup. */ /*#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ)*/ /* For divider */ //设置DEC中断触发的频度，与HZ相关。 outb_pit(LATCH >> 8 , PIT_CH0); /* MSB */ break;
时钟中断过了HZ会调用time_interrupt中断处理函数，而在时钟中断会调用如下函数
void tick_handle_periodic(struct clock_event_device *dev) clockevents_program_event(dev, next, ktime_get()) =>delta = ktime_to_ns(ktime_sub(expires, now)); if (delta <= 0) return -ETIME; dev->next_event = expires; if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) return 0; if (delta > dev->max_delta_ns) delta = dev->max_delta_ns; if (delta < dev->min_delta_ns) delta = dev->min_delta_ns; clc = delta * dev->mult;//mult和shift跟HZ强相关 clc >>= dev->shift; return dev->set_next_event((unsigned long) clc, dev); //.set_next_event = pit_next_event, 对于X86来说 =>int pit_next_event(unsigned long delta, struct clock_event_device *evt) outb_pit(delta & 0xff , PIT_CH0); /* LSB */ outb_pit(delta >> 8 , PIT_CH0); /* MSB */ 对于PPC来说 =>int decrementer_set_next_event(unsigned long evt, struct clock_event_device *dev) __get_cpu_var(decrementers).next_tb = get_tb_or_rtc() + evt; set_dec(evt);
Linux内部的时钟处理机制全面剖析
http://os.51cto.com/art/200709/89522_all.htmlinux kernel 时钟系统的前世今生
https://blog.csdn.net/skyflying2012/article/details/44727409linux调度器源码分析 - 运行(四)
https://www.cnblogs.com/tolimit/p/4335681.htmllinux HZ Tick Jiffies
https://blog.csdn.net/bdc995/article/details/4144031关于linux中定时器timer的宏定义LATCH的解释
http://blog.chinaunix.net/uid-23951161-id-206711.htmlLinux内核的时钟中断（2）
https://blog.csdn.net/m617105/article/details/40921087把握linux内核设计思想（六）：内核时钟中断
https://blog.csdn.net/shallnet/article/details/47132861