Introduction . The concept of resources in operating systems .
Plan:
1. In the operating system resource concept .
2. Description of resource classes.
3. Classify resources by characteristics.
In general, any object that is consumed (its), has a certain value for consumers, is a resource . Resources are limited and unlimited , depending on the unit in which they are allocated in the reserve . The fact that a resource is limited leads to vital needs among consumers. In order to regulate needs, resources must be distributed among consumers according to certain rules that will satisfy them to a high degree.
Description of resource classes.
The general classification of resources can be imagined as follows:
1. depending on the reality of existence: physical and virtual
2. Depending on the ability of the properties to expand: elastic and rigid
3. Depending on the level of activity: active and passive
4. Depending on the time of existence: primary and secondary
5. In terms of structure: simple and complex
Description of resource classes.
6. By type: produced and consumed
7. by form of implementation: soft and hard
8. Depending on the functionality: expensive and cheap
9. Depending on the nature of use: parallel and sequential.
Physical resources are resources that actually exist and that, when distributed among users, acquire (retain) their own physical properties.
A virtual resource is a different model of a physical resource. A virtual resource does not exist as the user imagines it.
A resource that allows virtualization, that is, the ability to expand its properties, is called flexible or elastic . A rigid resource is a resource that does not allow virtualization due to its internal properties.
When using an active resource, it applies or causes to be changed operations that change other resources or processes (or itself). A passive resource does not have this property. Possible operations are performed on such an object, during which its state changes, that is, its internal or external characteristics. The central processor is an active resource, and memory allocated on demand is a passive resource.
Depending on the level of activity resources
Resources
The distinction based on the “time of existence” feature is made based on the dynamics of the processes that use them. If a resource exists in the system before the process is born and can be accessed during the process’s existence, then this resource is permanent for that process. A process that uses a temporary resource can be dynamically created and destroyed in the system during its existence, either by the process itself or by other processes—system or user processes.
Level of importance of resources
1. providing the necessary functionality and 2. increasing the flexibility in managing processes and allocating resources. For this, primary and secondary resources are allocated. A resource is primary for a specific process, if, without its allocation, the process cannot develop. Such resources include, first of all, the central processor and operational memory. If the resources allow alternative development of the process when they are not allocated, such resources are called secondary resources. (mn, MD.ML).
Resources
The division of resources into expensive and cheap resources follows from the implementation of the principle of functional redundancy in their allocation. The user is faced with a choice - to quickly get the necessary resource and pay a high price for this service, or to wait for the allocation of the required resource and pay a low price when using it. If there are alternative resources in the system, various prices for their use are introduced.
Resources
The characteristic obtained in terms of structure indicates that the resource has some structure. If the resource does not consist of constituent elements and is taken as a whole when distributed, it is called simple . A complex resource is characterized by a certain structure. It consists of a series of elements that have a certain characteristic in its composition. A simple resource can be busy or free if it is allocated for use by some process. A complex resource is in the “free” state if none of its elements are allocated for use. If all of its elements are available for use, it is in the “busy” state; if only a portion of the resource elements are allocated, then the resource is “ partially busy .”
Possibility of recovery
Depending on the possibility of recovery , resources are divided into extractable and consumable.
It is assumed that the user-process performs three types of actions with respect to each resource: request, use, and release. If the actions performed by the system in allocating a resource can be performed in a repetitive “request-use-release” sequence, then such a resource is called a productive resource . After it is returned, it can be used by another process.
Therefore, if the appearance of a resource change after each use is not taken into account, the resource life can be considered infinitely large or sufficiently large until it loses its functional properties. It is correct to perform operations on resources of a certain category in the following order: release-demand-use, after which the resource, which is called consumed , is removed from the sphere of consumption (i.e., the relationship between the producer and the consumer). The lifetime of a consumed resource, that is, the time between the execution of the release and use operations, is determined and is finite. The resources consumed by the producer process and the consumer process behave as if they were temporary.
Nature of the resource and (or) the rule for allocating the resource used
several processes is characterized by a parallel or sequential use scheme. A sequential scheme implies the execution of the following fixed chain of actions “request-execute-release” in time with respect to the resource, which is called sequentially used . For parallel processes, such a chain of actions consists of a critical area, and they must be performed according to a predetermined rule of mutual negation. Therefore, resources that are used sequentially and are shared between several parallel processes are called critical resources . A parallel scheme involves the use of a single resource by multiple users at the same time, and is therefore called
Resources
Implementation is formally divided into soft and hard resources. Hard resources are understood as human resources, hardware components of the machine, all other resources are soft resources . The difference between hard and soft resources, in addition to complexity and cost, is their resilience to failures and failures and their ability to restore their functionality. In the class of soft resources , we distinguish two types: software and information resources .