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Multithread and Multiprocess

Multithreading

Advantages of Multithreading

When tasks that were previously handled concurrently using processes are implemented with threads, memory space and system resource consumption are reduced
When communication between threads is needed, instead of using separate resources, data can be exchanged using the global variable space or the dynamically allocated Heap area
- Therefore, inter-thread communication methods are much simpler compared to inter-process communication methods
A thread's context switch is faster than a process's context switch because there is no need to flush the cache memory
- As a result, the system's throughput improves,
- resource consumption decreases,
- and the program's response time naturally shortens
Because of these advantages, tasks are divided into threads within a single process

Problems with Multithreading

When programming based on multi-process, there are no shared resources between processes, so there is no situation where the same resource is accessed simultaneously. However, when programming based on multi-threading, this must be taken into account
- Since different threads share data and heap areas, one thread may access variables or data structures being used by another thread and read or modify incorrect values
Therefore, synchronization is necessary in a multi-threading environment
- Synchronization controls the order of task processing and access to shared resources.
  - but, this can lead to bottleneck issues, which increases the likelihood of performance degradation
    - Therefore, bottlenecks caused by excessive locks should be reduced
In a multi-thread environment, when multiple threads try to share a single resource, problems such as Deadlock can occur

Multithread vs Multiprocess

Multi-thread
- Advantages
  - Multi-threading occupies less space than multi-process and has faster context switching,
- Disadvantages
  - If one thread terminates due to an error, all threads may terminate, and
  - It has synchronization issues
Multi-process
- Advantages
  - In the multi-process approach, even if one process dies, other processes are not affected and continue to run normally,
- Disadvantages
  - It requires more memory space and CPU time than multi-threading
Summary
- Multi-thread and multi-process are the same in that they perform multiple tasks simultaneously,
  - but they are suited or unsuited depending on the system they are applied to
- Therefore, the appropriate operating method should be selected and applied based on the characteristics of the target system