Threading vs. Multiprocessing

https://qiita.com/shotaTsuge/items/0ad41fcee63a00a52f68

@shotaTsuge

posted at 2015-12-01

updated at 2015-12-02

beginner

,

memorandum

,

The Basics

I've decided to start over with MySQL from the basics for 6 months, and I'll post what I've learned during that time on Qiita.

Rough differences between threads and multiprocesses

One major difference is that child threads share heap (global program data) with their parent, whereas

child processes do not share.

Advantages and disadvantages of threads

Advantages

Low memory usage.

No need for sophisticated techniques to access server global data.

Even when data is modified by concurrent threads, only the relevant section needs to be protected using mutual exclusion locks (mutex).

Heap segments do not need to be copied and can be created in much less time than processes

Scheduler context switches take less time for the kernel than processes

Disadvantages

One thread crash can affect the entire server

Easy to make programming mistakes

Synchronization bugs in threaded servers (due to shared address space)

Mutex contention can be difficult to contain (causing excessive context switches)

Advantages and disadvantages of multiprocessing

Advantages

Even if there is a rogue server process, the entire server is not affected

Since only one thread of execution needs to be kept in mind, programming errors are less likely to occur

Easy to reproduce bugs, since phantom bugs (bugs that cannot be reproduced intentionally) are unlikely to occur.

Individual processes have their own address space, so interactions between processes are not large.

Disadvantages

When a child process branches, a large memory segment may be copied unnecessarily.

Data sharing between processes is time-consuming, and access to server global data is cumbersome

Imposes more overhead on the kernel to create processes

Parent process data segments must be copied

Context switches between processes consume a lot of time

Considerations

If you need to share a large amount of data between connection handlers (high programming skill), I personally thought that a threaded server I personally think that a threaded server is a good choice.

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Shota Tsuge

Shota Tsuge

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