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Fix Typo

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Fixes a typing mistake
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rajbhar 2017-04-15 17:58:46 +05:30 committed by proninyaroslav
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Timers/timers-3.md
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@ -70,7 +70,7 @@ By default, there is the `CONFIG_HZ_PERIODIC` kernel configuration option which
The first is to omit scheduling-clock ticks on idle processors. To enable this behaviour in the Linux kernel, we need to enable the `CONFIG_NO_HZ_IDLE` kernel configuration option. This option allows Linux kernel to avoid sending timer interrupts to idle processors. In this case periodic timer interrupts will be replaced with on-demand interrupts. This mode is called - `dyntick-idle` mode. But if the kernel does not handle interrupts of a system timer, how can the kernel decide if the system has nothing to do?
Whenever the idle task is selected to run, the periodic tick is disabled with the call of the `tick_nohz_idle_enter` function that defined in the [kernel/time/tick-sched.c](https://github.com/torvalds/linux/blob/master/kernel/time/tich-sched.c) source code file and enabled with the call of the `tick_nohz_idle_exit` function. There is special concept in the Linux kernel which is called - `clock event devices` that are used to schedule the next interrupt. This concept provides API for devices which can deliver interrupts at a specific time in the future and represented by the `clock_event_device` structure in the Linux kernel. We will not dive into implementation of the `clock_event_device` structure now. We will see it in the next prat of this chapter. But there is one interesting moment for us right now.
Whenever the idle task is selected to run, the periodic tick is disabled with the call of the `tick_nohz_idle_enter` function that defined in the [kernel/time/tick-sched.c](https://github.com/torvalds/linux/blob/master/kernel/time/tich-sched.c) source code file and enabled with the call of the `tick_nohz_idle_exit` function. There is special concept in the Linux kernel which is called - `clock event devices` that are used to schedule the next interrupt. This concept provides API for devices which can deliver interrupts at a specific time in the future and represented by the `clock_event_device` structure in the Linux kernel. We will not dive into implementation of the `clock_event_device` structure now. We will see it in the next part of this chapter. But there is one interesting moment for us right now.
The second way is to omit scheduling-clock ticks on processors that are either in `idle` state or that have only one runnable task or in other words busy processor. We can enable this feature with the `CONFIG_NO_HZ_FULL` kernel configuration option and it allows to reduce the number of timer interrupts significantly.