A computing architecture known as symmetric multiprocessing (SMP) involves connecting two or more processors to a single memory and operating system (OS) instance. SMP uses multiple processors to finish a task. This is done with the help of a host operating system, which handles the allocation, execution, and control of processors. This article explains everything you need to understand about symmetric multiprocessing. We also explained the differences between Asymmetric vs Symmetric Multiprocessing to avoid mixing them up.
Let’s dig in!
What Is Multiprocessing?
You need to have a firm grasp of the concepts of Processing and Processor to fully appreciate them. Our computer’s CPU (Central Processing Unit) is the brains behind the operation, receiving signals from the computer’s many input and output devices and processing them into action. The central processing unit (CPU) is a prime example of a single processor.
Multi-Processing refers to the employment of more than one central processing unit (CPU) in a single device. There are two distinct kinds of multi-processors, distinguished by the tasks they perform.
- Asymmetric
- Symmetric
What Is Symmetric Multiprocessing?
When many processors access the same memory and OS, they are said to be SMP (symmetric multiprocessing). The processors in a symmetric multiprocessing setup share the same data path or I/O bus. All the computers are controlled by a single OS installation. When numerous users access the same database in a small number of transactions, SMP systems excel over massively parallel processing (MPP) systems in terms of performance and efficiency. SMP systems, in contrast to MPP systems, can dynamically distribute work among computers to process more requests in less time.
SMP is a type of multiprocessor computer architecture that uses a group of processors that are all exactly the same. Each CPU has full access to the system’s shared main memory and all I/O ports. Nowadays, SMP computers are supported by the majority of OSes. In the past, users required specialized programming knowledge to effectively utilize SMP.
Features of Symmetric Multiprocessing (SMP)
- Tightly coupled multiprocessing is another name for symmetric multiprocessing, in which all of the CPUs are linked at the bus level and can access the same memory.
- Symmetric multiprocessing relies on each parallel processor having its own cache memory to lessen the load on the system bus and speed up data access.
- One processor in a symmetric multiprocessing system can run code for any program, regardless of where the associated data is stored in memory. The sole caveat is that a process cannot run on many processors at once.
- Since the operating system can easily manage up to 16 processors on a symmetric multiprocessing system, this is typically the upper limit.
Uses of Symmetric Multiprocessing
The following are examples of where symmetric multiprocessing has been useful:
- Time-sharing systems, which have many processes operating in parallel, benefit greatly from symmetric multiprocessing. Therefore, symmetric multiprocessing can be used to schedule these operations on parallel processors.
- Without multithreaded programming, symmetric processing is not very helpful on home computers. The parallel processors can be used to schedule several threads.
- Multithreaded systems that share processing resources with other users can benefit from symmetric multiprogramming as well.
How Is Symmetric Multiprocessing Used?
System architectures based on symmetric multiprocessing are typically deployed in high-demand data centers. In these setups, running application activities and processes requires a lot of processing power. Simple Multiprocessor (SMP) architectures are widely used in modern multicore computers.
Systems with multiple threads can benefit the most from SMP. The term “time-sharing” refers to the practice of allocating a single computer’s time to several users simultaneously. The multithreading capability of modern central processing units (CPUs) allows for the execution of several threads within a single CPU process. To be more precise, multithreading allows numerous threads of instructions to run simultaneously while sharing the same CPU.
Because it allows for the distribution of computing resources across several users and the execution of multiple processes in parallel, SMP is used in time sharing. SMP facilitates this by allowing multiple tasks to run simultaneously on separate CPUs. For the same reason that SMP is used in multithreading—to distribute the various threads across several processors—it is also employed in multithreading.
However, SMP is rarely utilized on PCs or in software that has not been updated to support multithreaded programming. To schedule threads on separate parallel processors, applications and programs must be written with multithreading in mind.
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What Are the Advantages and Disadvantages of SMP?
Some benefits of using symmetric multiprocessing are as follows:
- Higher levels of throughput: Task execution times can be reduced by using a cluster of processors.
- Reliability: A single processor failure does not bring down the entire system. However, productivity may still suffer.
- Cost-effective: Since the processors in an SMP system share data storage, power supply, and other resources, it is a more cost-effective long-term solution to boost system throughput than a single processor system.
- Performance: An SMP computer system outperforms a single-processor system dramatically due to the higher throughput possible with several processors.
- Creating and running computer programs: Since a program’s performance is roughly the same regardless of whatever processor it’s being executed on, creating and running code on an SMP system is a breeze.
- Multiple processors: It is possible to add more processors to a system if it is taking too long to finish a certain task.
Drawbacks to SMP That You Should Be Aware of
- Memory expense: Main memory needs to be large enough to accommodate all the processors in an SMP system because they all share the same data.
- Compatibility: Operating systems, software, and applications need to be SMP-friendly for the architecture to function properly.
- Complicated OS: In a system with multiple processors, the OS controls them all. Since the OS must manage all the available processors while running in resource-intensive computer settings, its design and management might be difficult.
Asymmetric vs Symmetric Multiprocessing
The central processing unit is an essential component of any computer. It can handle input-output operations as well as mathematical and logical calculations. It also generates signals that are used to coordinate the actions of other components. The two forms of multiprocessing are asymmetric vs symmetric multiprocessing. When there is more than one processor available, we say that the system is “multiprocessing.” In symmetric multiprocessing, the memory of each CPU is shared equally. A single master processor in an Asymmetric Multiprocessing system manages the whole data hierarchy.
Differentiating between symmetric vs asymmetric multiprocessing in the OS is the focus of this essay. But before we get into it, we need to make sure you understand the distinction between symmetric vs asymmetric multiprocessing in the OS.
Review of Symmetric Multiprocessing
When all processors are used for OS processes, this is known as symmetric multiprocessing. The shared memory is used for communication across all processors, and there is no master-slave relationship like in asymmetric multiprocessing. Processes are initiated by the processors from the shared ready queue, while each CPU may also have its own dedicated queue of ready-to-execute instructions. The scheduler is responsible for preventing two CPUs from working on the same job at the same time.
Load balancing, fault tolerance, and reduced CPU bottleneck risk are all benefits of symmetric multiprocessing. It’s tricky because with Symmetric Multiprocessing, all the CPUs use the same memory, and losing one of them affects performance.
Review of Asymmetric Multiprocessing
Asymmetric multiprocessing involves a master-slave relationship between the processors, with the master processor exercising command over the slave processors. The master processor can delegate certain duties to the slave processors, or the master processor might hand off the entire process to the slaves. The data structure is controlled by the master processor. The master processor is responsible for coordinating the system’s activities and handling all input/output operations.
One of the slave processors will take over if the master processor fails. One of the slave processors will take over if the other one fails. The data format and a single processor make all system actions very easy to understand and execute. Consider four central processing units labeled C1, C2, C3, and C4. C4 is the primary processor and is responsible for dividing up work among the others. Suppose that C1, C2, and C3 are all assigned to respective processes P1, P2, and P3, respectively. Each CPU will solely focus on the tasks that have been assigned to it.
The Key Difference Between Symmetric vs Asymmetric Multiprocessing
When it comes to operating systems, Symmetric vs Asymmetric Multiprocessing differ in a number of crucial ways. The following are some of the most notable OS-level distinctions between Symmetric vs Asymmetric Multiprocessing:
- Many processors working together to run the same set of programs in the same memory and operating system is called symmetric multiprocessing. However, asymmetric multiprocessing describes the execution of many programs in a master-slave fashion.
- In symmetric multiprocessing, each CPU can select work from either a shared ready queue or its own dedicated queue. In asymmetric multiprocessing, the master processor gives jobs to the slave processors.
- In symmetric multiprocessing, processors exchange data via shared memory. In Asymmetric Multiprocessing, on the other hand, the processors don’t need to talk to one another because they’re all under the command of a single master processor.
- With an asymmetric multiprocessor, only the master processor needs access to the underlying data structure. However, symmetric multiprocessors are challenging due to the need for synchronization across all units.
- All Symmetric Multiprocessing processors share the same underlying design. However, with an asymmetric multiprocessor, the structure of the processors may be different
- In symmetric multiprocessing, each CPU can access either a common pool of ready processes or maintain its own queue of ready tasks. Instead, processes are distributed across slave processors in asymmetric multiprocessing.
- Comparatively, asymmetric multiprocessing systems cost less than their symmetric counterparts.
- Asymmetric multiprocessing systems are also less complicated to develop and keep up with than their symmetric counterparts.
What Is Symmetric Multiprocessing in Parallel Computing?
Computers with a symmetrical multiprocessing (SMP) architecture have two or more processors that work together to run a single instance of an operating system and share the machine’s memory and other resources. The memory, input/output, and external interrupts are shared equally across all the processors.
What Is An Asymmetric Multiprocessing System?
An asymmetric multiprocessing system is a computer architecture in which the many connected CPUs are not all given the same priority. The operating system tasks in asymmetric multiprocessing are handled by a single master processor.
What Are the Characteristics of Symmetric Multiprocessors?
- Identical: All the processors are treated equally i.e. all are identical.
- Communication: Shared memory is the mode of communication among processors.
- Complexity: These are complex in design, as all units share the same memory and data bus.
- Expensive: They are costlier in nature.
What Is Symmetric Multiprocessing Also Known As?
Symmetric multiprocessing is also called closely coupled multiprocessing because all the CPUs are connected at the bus level and can access the same memory. In symmetric multiprocessing, each of the parallel processors has its own cache memory, cutting down on system bus traffic and improving data access times.
What Is the Difference between Symmetric Multiprocessing and Massively Parallel Processing?
The structure of the system is what differentiates SMP from MPP. Each processor in an SMP system uses the same pool of shared memory and bandwidth. Each processor in an MPP system has its own set of non-shared resources.
Final Thoughts
Symmetric and asymmetric multiprocessing are two possible forms, with distinct operational characteristics. All processors in symmetric processing are treated as equals, while in asymmetric processing, a master-slave dynamic exists. However, the system’s speed and performance are improved by using two processors. We do hope this article was insightful. Let’s hear from you in the comment section below!
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