suitefoki.blogg.se - Linux real time timeslice

#LINUX REAL TIME TIMESLICE UPDATE#
#LINUX REAL TIME TIMESLICE DRIVER#
#LINUX REAL TIME TIMESLICE FULL#

An example is a display warning for low fuel in a vehicle, or a moderate loss of tire pressure. These systems have built in tolerances and are easier to implement. Soft Real Time systems face penalties for missing the timing requirement, but do not cause such bad effects.

#LINUX REAL TIME TIMESLICE FULL#

Another is full application of brakes in a vehicle upon detection of an obstacle in the way, or sudden full pressure on brake pedal by the driver. Some examples of these are airbag deployment time after the sensor presents to the system, or a heart defibrillator activating after detection of an arrhythmia. Hard Real Time systems present catastrophic, or even fatal consequences if the requirement is not met. We usually break Real Time into 2 categories.

The response time must be deterministic, meaning repeatable and verifiable. What distinguishes a Real Time System from an ordinary system, such as your PC? A Real Time System must respond to external stimuli, within a predetermined time. Also, high speed Ethernet is required if networking is involved, and possibly wireless communication capabilities as well. Generally, these are now part of the many highly integrated CPU ASIC devices.

Optional, but becoming more and more mandatory, are Mass Storage interfaces – SATA, MSATA, SD card, Micro SD card, CFAST card, USB.

Power Monitor – Usually included in the CPU, generates an interrupt and Reset at voltage drops.

The finer the resolution the more accurate the timing. Acts as the system tick counter for all timing events.

System HW timer– which is usually part of the CPU.

Interrupt controller– which usually is part of the CPU.

#LINUX REAL TIME TIMESLICE DRIVER#

PC BIOS also holds code to handle software interrupt calls from, main code, as well providing low level, device driver hooks. You will see this in every PC based design where the BIOS does all the initial hardware scanning and aids in low level HW initialization. This usually holds the initial low level boot code, loader code, and sometimes the Basic IO System (BIOS). The controller for the DRAM is usually part of the CPU, Flash Memory or ROM.

Ram Memory and Controller– Usually DRAM, used to run programs and for transient data storage.

Executes a set of instructions in a program (process or application) created by the system programmer.

CPU – Various types such as RISC or CISC, single core or multi-core, fully integrated ASIC type controllers.Setting too long will cause poor response to short interactive processes.Ī quantum around 100 m sec is usually reasonable.Real Time Embedded Systems generally consist of Hardware and Software (More often referred to as Firmware). Too short will cause too many process switches and will lower CPU efficiency. The unlucky last (P10) will have to wait for 5 sec, assuming that all others use their full time slices. If P1 starts executing for first time slice then P2 will have to wait for 1/2 sec and waiting time for other processes will increase. Let the time slice size be set to say 500 m sec and 10 processes are in the ready queue. Thus CPU has to spend 5 m sec on process switching again and again wasting 20% of CPU time.

#LINUX REAL TIME TIMESLICE UPDATE#

Switching from one process to another requires a certain amount of time to save and load registers, update various tables and lists etc.Ĭonsider, as an example, process switch or context switch takes 5 m sec and time slice duration be 20 m sec.

So the choice of time quanta is a very important design decision. Too short quantum causes too many process/context switches and reduces CPU efficiency. When the time quantum is very large, the Round Robin policy becomes a FCFS policy. The performance of time slicing policy is heavily dependent on the size/duration of the time quantum. Long processes may require several quanta. Short processes may be executed within a single time quantum. In this type of scheduling, CPU time is divided into slices that are to be allocated to ready processes. The aim of Round Robin scheduling or time slicing scheduling is to give all processes an equal opportunity to use CPU. It is also termed as Round Robin scheduling. Question: Explain time slicing? How its duration affects the overall working of the system?Īnswer: Time slicing is a scheduling mechanism/way used in time sharing systems.