Operating systems may feature up to 3 distinct types of schedulers: a long-term scheduler (also known as an admission scheduler or high-level scheduler), a mid-term or medium-term scheduler and a short-term scheduler . The names suggest the relative frequency with which these functions are performed.
The long-term, or admission, scheduler decides which jobs or processes are to be admitted to the ready queue; that is, when an attempt is made to execute a program, its admission to the set of currently executing processes is either authorized or delayed by the long-term scheduler. Thus, this scheduler dictates what processes are to run on a system, and the degree of concurrency to be supported at any one time - ie: whether a high or low amount of processes are to be executed concurrently, and how the split between IO intensive and CPU intensive processes is to be handled. In modern OS's, this is used to make sure that real time processes get enough CPU time to finish their tasks. Without proper real time scheduling, modern GUI interfaces would seem sluggish.
Long-term scheduling is also important in large-scale systems such as batch processing systems, computer clusters, supercomputers and render farms. In these cases, special purpose job scheduler software is typically used to assist these functions, in addition to any underlying admission scheduling support in the operating system.
The mid-term scheduler temporarily removes processes from main memory and places them on secondary memory (such as a disk drive) or vice versa. This is commonly referred to as "swapping out" or "swapping in" (also incorrectly as "paging out" or "paging in"). The mid-term scheduler may decide to swap out a process which has not been active for some time, or a process which has a low priority, or a process which is page faulting frequently, or a process which is taking up a large amount of memory in order to free up main memory for other processes, swapping the process back in later when more memory is available, or when the process has been unblocked and is no longer waiting for a resource.
In many systems today (those that support mapping virtual address space to secondary storage other than the swap file), the mid-term scheduler may actually perform the role of the long-term scheduler, by treating binaries as "swapped out processes" upon their execution. In this way, when a segment of the binary is required it can be swapped in on demand, or "lazy loaded".
The short-term scheduler (also known as the CPU scheduler) decides which of the ready, in-memory processes are to be executed (allocated a CPU) next following a clock interrupt, an IO interrupt, an operating system call or another form of signal. Thus the short-term scheduler makes scheduling decisions much more frequently than the long-term or mid-term schedulers - a scheduling decision will at a minimum have to be made after every time slice, and these are very short.
This scheduler can be preemptive, implying that it is capable of forcibly removing processes from a CPU when it decides to allocate that CPU to another process, or non-preemptive (also known as "voluntary" or "co-operative"), in which case the scheduler is unable to "force" processes off the CPU.
What two types of data can be collected? Describe eac.
A CPU scheduler maximizes CPU utilization. It can do the scheduling based on two types, which is either a preemptive or a non-preemptive scheduling.
What is the difference between the three types of ballistics
You can open any file with C, since it does not distinguish between file types. It's the way you read from the file.
The features that distinguish the three types of muscular tissue are structure, location, function, and means of activation. Structure can include straiated, smooth or rough. Location is where in the body . Function can include beating the heart, lifting an object. Finally means of activation could be voluntary or involuntary.
Transverse mutation Deletion Insertion These are three types of chromosomal mutations.
Properties are characteristics of a sample of matter that is fixed by its state. They are the features that distinguish the difference between types of matter.
Phonologists distinguish between three main categories of phonemes: consonants, vowels, and diphthongs.As a speaker makes a vowel sound, the vocal tract is unobstructed and air leaves the lungs in a constant stream: /o/, /u/, /i/.
good, bad, in-between
between functional units
Usually the brand and model number will give it away, or the types of audio hookups.