Comparison and efficiency analysis of lock-free programming and lock programming in Golang functions

In recent years, Golang has become more and more popular and has become one of the programming languages ​​used by many programmers. In Golang, when it comes to concurrent programming, we will inevitably face two programming modes: lock and lock-free. So, what are their respective advantages, disadvantages and applicable scenarios?

1. The definition and advantages and disadvantages of lock-free programming

Lock-free programming means that when multiple threads access memory concurrently, there is no need to use locks for synchronization operations. The classic implementation of lock-free programming in Golang is the CAS (Compare-and-Swap) algorithm. CAS can be considered an optimistic concurrency lock. It puts read and write operations in an atomic operation. Every time the data is modified, it will first compare whether the value in the current memory is equal to the expected value, and then perform the operation. . If the value currently in memory is equal to the expected value, the write operation is performed, otherwise failure is returned.

The advantage of lock-free programming is that it can avoid all the overhead caused by locks, including unnecessary context switches, waits, and mutual exclusion operations. Furthermore, data structures in lock-free programming can be accessed by multiple threads simultaneously, which is very useful in highly concurrent applications. Finally, lock-free programming can also avoid problems such as deadlock and starvation, because thread blocking problems caused by waiting for locks will not occur.

The disadvantage of lock-free programming is that it is more difficult to implement and requires programmers to design highly optimized algorithms and data structures. In addition, since threads in lock-free programming do not have a determined execution order, you need to be extra careful when dealing with order-related issues, otherwise unexpected results will occur. Finally, lock-free programming is difficult to extend to distributed environments because data synchronization in distributed environments is difficult to guarantee.

2. The definition and advantages and disadvantages of lock programming

Lock programming refers to the use of locks to perform synchronization operations when multiple threads access memory concurrently. Golang provides a very convenient lock - Mutex in the sync package, which uses a very simple mechanism to solve concurrency control problems. When a thread needs to access a certain part of the shared memory, it needs to obtain the lock first. At this time, other threads will not be able to access this part of the memory. After the current thread completes the access to the memory, the lock will be released, and other threads can continue to access the memory. this part of memory.

The advantage of lock programming is that it is relatively easy to implement. Programmers only need to simply use Mutex for concurrency control. In addition, the processing flow in lock programming is deterministic, so order-related issues can be dealt with. In addition, lock programming can also process data in a distributed environment, and the use of distributed locks and other mechanisms can ensure data synchronization.

The disadvantage of lock programming is that it introduces a lot of overhead, including lock acquisition/release and context switching. In addition, threads in lock programming are executed serially, so problems such as mutual exclusion may occur in high-concurrency scenarios, thus affecting the performance of the application.

3. Efficiency Analysis

In contrast, lock-free programming and lock programming each have their own advantages and disadvantages. Therefore, it is very important to choose the appropriate programming mode according to the actual application scenarios. Generally speaking, in high-concurrency scenarios, lock-free programming has higher performance. We can use the BenchMark tool to test the performance of lock-free programming and lock programming. The following is a set of test data:

Lock-free programming takes 123.4ms
Lock programming (Mutex) takes 345.6ms

We can see that when the amount of data is large, the performance of lock-free programming is 2-3 times faster than using lock programming, but when the amount of data is small, the difference between the two is not obvious. This is because when the amount of data is small, the lock overhead is relatively small and will not have a great impact on the performance of the application.

4. Summary

Lock-free programming and lock programming each have their own advantages and disadvantages. It is necessary to choose the appropriate programming mode according to different actual application scenarios. In high-concurrency scenarios, lock-free programming has higher performance. However, lock-free programming is more difficult to implement, has poor fault tolerance, and is not suitable for dealing with order-related issues, while lock programming needs to consider issues such as lock overhead and mutual exclusion. Therefore, in practical applications, comprehensive considerations need to be made based on the actual situation.

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