What is the difference between rtos and gpos

RTOS on the other hand is designed to deliver an accurate output within the expected timeline which as stated earlier, is akin to the time taken for the blink of an eye. In the rarest of instances of an RTOS delaying response, catastrophic events may occur. Hence, in an embedded system, an RTOS shoulders a highly critical responsibility. RTOS is specifically required for applications which have time-critical requirements and need to respond instantly.

It is used in systems where multiple operations are being executed at the same time and resources are being shared. In the language of computer architecture, a Multithreading defines the ability of a processing unit to manage multiple threads concurrently. This approach helps in ensuring efficient. At its best, an embedded RTOS creates an illusion of parallel execution by rapidly switching between the executing tasks.

It enables you to inculcate a new level of abstraction into applications which paves the way for more complexity to be built into them. It gives the product development teams complete control over multithreading, thus enabling deterministic real-time behavior. Traditionally, in case of complex applications, development teams relied on custom states and logic for successful execution of the control mechanism. However, as the complexity of electronic systems increased manifold, this became more error-prone and difficult to maintain.

All tasks within an embedded RTOS have specific timelines associated with them. It might complete the procedure without glitches or may even hang during it since several tasks are being executed in parallel. Tasks must be completed within the strict deadlines and in parallel, in order for the system to honor the SLA.

For example, in an automatic air-bag control system, as soon as the vehicle senses a sharp jerk, the air-bags should be activated without the delay of even a second. This is because even a milli-second of delay can lead to a serious injury for the driver. While evaluating an embedded RTOS that can perfectly fulfill the business and technology requirements of an embedded application, your team should ensure that the RTOS in considerations supports a set of critical features.

The procedure involves several steps that should be carried out with care in order to make the system function smoothly. Some kernels can be considered to meet the requirements of a real-time operating system.

However, since other components, such as device drivers, are also usually needed for a particular solution, a real-time operating system is usually larger than just the kernel. Before going deep down, it will be good if you read this article from Howstuffworks- about Operating Systems. Many Embedded interviewer ask this question. Well, never use these words. More appropriate answer would be ROTS are deterministic. RTOS guarantee you that particular operation would complete at the worst this much time.

This is the very basic criteria of being a RTOS. Its all about money, if you can save even 25 cents on one embedded device hardware, and embedded devices are sold in millions of units say memory card Companies can make millions of dollars. A GPOS is made for high end, general purpose systems like a personal computer, a work station, a server system etc. But an embedded system works on low hardware configurations usually — speed in the range of Megahertz and RAM in the range of Megabytes.

A GPOS being too heavy demands very high end hardware configurations. This ensurers the fairness with which programs are executed. But it gives no gaurntee that the high priroirty thread will be given preference to the lower priority one.

In some cases the OS may decay the priority or dyanamically adjust of the thread in order to achive fairness. Lets take the case of task scheduling first. GPOS is programmed to handle scheduling in such a way that it manages to achieve high throughput. Here throughput means — the total number of processes that complete their execution per unit time. In such a case, some times execution of a high priority process will get delayed inorder to serve 5 or 6 low priority tasks.

High throughput is achieved by serving 5 low priority tasks than by serving a single high priority one. Where as in an RTOS — scheduling is always priority based. Most RTOS uses pre-emptive task scheduling method which is based on priority levels. Here a high priority process gets executed over the low priority ones. A high priority process execution will get override only if a request comes from an even high priority process. In General, the more the number of threads the more time GPOS takes to schedule and start executing the the thread.

In highly time constraints RTOS system this delay could be devise. All it tells is, the Algorithms of ROTS kernel should be deterministic and should be able to perform even if no of resources are more.

The more number of threads to schedule, latencies will get added up! In ROTS other hand, kernel opreations are preemptive. It means low priority task will be preemted even if its executing any system call. There would be some delays some times, but a carefully designed RTOS will have those delays very small. And one more important point, even for these delatils the upper bound of delay time would be well defined.

For example:- a request from a driver or some other system service comes in, it is treated as a kernel call which will be served immediately overriding all other process and threads. In an RTOS the kernel is kept very simple and only very important service requests are kept within the kernel call.

All other service requests are treated as external processes and threads. All such service requests from kernel are associated with a bounded latency in an RTOS. This ensures highly predictable and quick response from an RTOS. To achieve this goal, the RTOS kernel must be simple and as elegant as possible. Only services with a short execution path should be included in the kernel itself. Any operations that require significant work for instance, process loading must be assigned to external processes or threads.

Such an approach helps ensure that there is an upper bound on the longest nonpreemptible code path through the kernel. In a few. GPOSs, such as Linux 2. However, the intervals during which preemption may not occur are still much longer than those in a typical RTOS, the length of any such preemption interval will depend on the longest critical section of any modules incorporated into the kernel for example,networking and file systems. Moreover, a preemptive kernel does not address other conditions that can impose unbounded latencies, such as the loss of priority information that occurs when a client invokes a driver or other system service.

A process with less priority can be executed first. Task scheduler uses fairness policy which enables the overall high throughput but offers no guarantee that high priority tasks will be executed first.

Now if you have a query or feedback then write us in the comments below. Real-Time Operating System RTOS is a type of operating system which is designed to run an application with very precise timing and a very high degree of reliability. Share this: Twitter Facebook.