Documentation/timers/highres.rst

8 https://www.kernel.org/doc/ols/2006/ols2006v1-pages-333-346.pdf
11 http://www.cs.columbia.edu/~nahum/w6998/papers/ols2006-hrtimers-slides.pdf
15 design of the Linux time(r) system before hrtimers and other building blocks
23 - hrtimer base infrastructure
24 - timeofday and clock source management
25 - clock event management
26 - high resolution timer functionality
27 - dynamic ticks
31 ---------------------------
40        - time ordered enqueueing into a rb-tree
41        - independent of ticks (the processing is based on nanoseconds)
44 timeofday and clock source management
45 -------------------------------------
48 code out of the architecture-specific areas into a generic management
69 clock event management
70 ----------------------
78 makes it extremely difficult to change the configuration of the system to use
81 to touch all the architecture-specific implementations in order to provide new
95 structure with clock-specific property parameters and callback functions. The
96 clock event management decides, by using the specified property parameters, the
97 set of system functions a clock event device will be used to support. This
98 includes the distinction of per-CPU and per-system global event devices.
100 System-level global event devices are used for the Linux periodic tick. Per-CPU
104 The management layer assigns one or more of the following functions to a clock
107       - system global periodic tick (jiffies update)
108       - cpu local update_process_times
109       - cpu local profiling
110       - cpu local next event interrupt (non periodic mode)
113 functions completely to the management layer. The clock management layer stores
143 -----------------------------------
145 During system boot it is not possible to use the high resolution timer
151 initialized, the system works in the usual low resolution periodic mode. The
156 configured for high resolution timers can run on a system which lacks the
169 decision is made per timer base and synchronized across per-cpu timer bases in
170 a support function. The design allows the system to utilize separate per-CPU
171 clock event devices for the per-CPU timer bases, but currently only one
172 reprogrammable clock event device per-CPU is utilized.
176 red-black tree to a separate double linked list and invokes the softirq
177 handler. An additional mode field in the hrtimer structure allows the system to
182 context is the avoidance of up to two context switches - from the interrupted
186 Once a system has switched to high resolution mode, the periodic tick is
187 switched off. This disables the per system global periodic clock event device -
190 The periodic tick functionality is provided by an per-cpu hrtimer. The callback
209 -------------
215 - hrtimer_stop_sched_tick
216 - hrtimer_restart_sched_tick
217 - hrtimer_update_jiffies
239 management control.