Linux Kernel Development by Love Robert

Linux Kernel Development by Love Robert

Author:Love, Robert [Love, Robert]
Language: eng
Format: mobi
Publisher: Addison-Wesley Professional
Published: 2010-06-21T16:00:00+00:00


3 Because of architectural and NTP-related issues, however, not just any value is acceptable for HZ. On x86, 100, 500, and 1000 all work fine.

A Tickless OS

You might wonder whether an operating system even needs a fixed timer interrupt. Although that has been the norm for 40 years, with nearly all general-purpose operating systems employing a timer interrupt similar to the system described in this chapter, the Linux kernel supports an option known as a tickless operation. When a kernel is built with the CONFIG_HZ configuration option set, the system dynamically schedules the timer interrupt in accordance with pending timers. Instead of firing the timer interrupt every, say, 1ms, the interrupt is dynamically scheduled and rescheduled as needed. If the next timer is set to go off in 3ms, the timer interrupt fires in 3ms. After that, if there is no work for 50ms, the kernel reschedules the interrupt to go off in 50ms.



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