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A tickless kernel is an operating system kernel in which timer interrupts do not occur at regular intervals, but are only delivered as required. [1]The Linux kernel on s390 from 2.6.6 [2] and on i386 from release 2.6.21 [3] can be configured to turn the timer tick off (tickless or dynamic tick) for idle CPUs using CONFIG_NO_HZ, and from 3.10 with CONFIG_NO_HZ_IDLE extended for non-idle ...
The process sets these time limits by calling alarm or setitimer. The time limit for SIGALRM is based on real or clock time; SIGVTALRM is based on CPU time used by the process; and SIGPROF is based on CPU time used by the process and by the system on its behalf (known as a profiling timer).
In contrast to the previous O(1) scheduler used in older Linux 2.6 kernels, which maintained and switched run queues of active and expired tasks, the CFS scheduler implementation is based on per-CPU run queues, whose nodes are time-ordered schedulable entities that are kept sorted by red–black trees. The CFS does away with the old notion of ...
In February 2003 Andrea Arcangeli put forward his idea for a Stochastic Fair Queueing I/O scheduler to Jens Axboe who then implemented it. Jens Axboe made improvements to his first implementation, calling the new version the Completely Fair Queueing scheduler, and produced a patch to apply it to the 2.5.60 development series kernel.
The location of process schedulers in a simplified structure of the Linux kernel. The Brain Fuck Scheduler (BFS) is a process scheduler designed for the Linux kernel in August 2009 based on earliest eligible virtual deadline first scheduling (EEVDF), [2] as an alternative to the Completely Fair Scheduler (CFS) and the O(1) scheduler. [3]
Timer 0 is used by Microsoft Windows (uniprocessor) and Linux as a system timer, timer 1 was historically used for dynamic random access memory refreshes and timer 2 for the PC speaker. [2] The LAPIC in newer Intel systems offers a higher-resolution (one microsecond) timer. [3]
Time-triggered systems can be viewed as a subset of a more general event-triggered (ET) system architecture (see event-driven programming).. Implementation of an ET system will typically involve use of multiple interrupts, each associated with specific periodic events (such as timer overflows) or aperiodic events (such as the arrival of messages over a communication bus at random points in time).
After servicing the events, the program then goes to sleep again for the next time interval. Certain kinds of heartbeat events or keep-alive signals can be generated by these kinds of programs. The sleep() function call can be repeatedly called for short periods of time to slow the execution of a running program or code.