struct hrtimer是用于高精度定时器(High-Resolution Timer,HRTimer)的结构体,其完整定义在<linux/hrtimer.h>中,用于内核中的高精度计时器事件。 it_real_fn函数同样定义在<linux/hrtimer.h>中,用作hrtimer的处理函数。其接受一个指向struct hrtimer类型的指针timer,表示触发了该实时定时器的定时器对象。函数返回一个e...
旧内核的定时器实现依赖于系统定时器硬件定期的tick,基于该tick,内核会扫描timer wheel处理超时事件,会更新jiffies,wall time(墙上时间,现实时间),process的使用时间等等工作。 新的内核不再会直接支持周期性的tick,新内核定时器框架采用了基于事件触发,而不是以前的周期性触发。新内核实现了hrtimer(high resolution tim...
clock 0:---clock0作为MONOTONIC使用ktime_get获取当前时间,是timerkeeper的xtime和wall_to_monotonic之和。 .base: c0531950 .index: 0 .resolution: 1 nsecs .get_time: ktime_get .offset: 0 nsecs---和MONOTONIC相比的offset。 active timers:---print_active_timers打印所有的hrtimer,按照时间排列,timerq...
若是禁用High-Resolution Timer,那么内核是在毫秒级别处理内部时间分片。 禁用掉High-Resolution Timer不会有问题,除非你的应用程序需要在纳秒级别处理时间分片。 如下摘自:Oracle Linux: How to Disable High-Resolution Timer (文档 ID 2207818.1) High-resolution timer is implemented on UEK[1234] and RHCK for O...
linux具有Dynamic Ticks和High Resolution Timer, 详细可以参考kernel/time/Kconfig下。 config TICK_ONESHOT bool config NO_HZ bool "Tickless System (Dynamic Ticks)" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS select TICK_ONESHOT
linux具有Dynamic Ticks和High Resolution Timer, 详细可以参考kernel/time/Kconfig下。 config TICK_ONESHOT bool config NO_HZ bool "Tickless System (Dynamic Ticks)" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS select TICK_ONESHOT
注意到,HRTIMER_MAX_CLOCK_BASES:4,.resolution: 1 nsecs表示当前内核是支持hrtimer的。 基本数据结构 ktime: union ktime {s64 tv64;#if BITS_PER_LONG != 64 && !defined(CONFIG_KTIME_SCALAR)struct {# ifdef __BIG_ENDIANs32 sec, nsec;# elses32 nsec, sec;# endif} tv;#endif}; ...
那纯树形结构呢?Linux 中最为广泛采用的一种二叉树恐怕就是 rbtree 了,从进程内存管理的VMA,到 CPU 调度的CFS,再到文件事件监听的 epoll,都有它的身影。同样地,rbtree 的结构也被 Linux 中以 nanosecond 为单位的 high-resolution timer (简称 hrtimer)所采用,其查找的复杂度为O(log n)。
You can configure agent computers to use a high-resolution timer when collecting performance data. The high-resolution timer ensures that all measurements are precise to within 1 millisecond. Before you begin The high-resolution timer is used by default on the Linux operating system. You do not ...
one may get the same time value twice; and that timers must wait for the next clock tick after the theoretical expiration time, to ensure that a timer never returns too soon. Note also that the granularity of the clock may be significantly coarser than the resolution of the data format us...