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This article mainly explains "cpu cache coherence in java what help programming," interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's take you to learn "CPU cache coherence in java what help programming"!

1. Data alignment access

Because short, int, long, and fractional groups may span 2 cache lines, the CPU will have to involve 2 cache lines when reading and writing, which is obviously inefficient. As for how to solve this problem in practice, I am going to write a separate article about java solution.

2. Maintain data spatial locality

The test results were given earlier in the efficiency difference test due to locality of data space, which said that adjacent data should be placed in a cache as much as possible and accessed according to continuous space.

3. Avoid pseudo-sharing when programming with multiple threads

In the previous java concurrent programming topic---false sharing also gave the test results, it said that there is no data competition in the business, but in the CPU bottom execution because the data read and written in the same cache line, resulting in a large number of cache misses affecting the execution efficiency. Here to use the volatile keyword to make a supplementary explanation, for java if there is no volatile keyword, because there is no competition between variables, even in the same cache line, each thread only reads and writes cache copies of their variables, which is determined by the characteristics of jvm. When the volatile keyword is added, it is necessary to synchronize the data with the memory. If the variables read and written by each other are in the same cache line, this can be explained by MESI cache coherence principle, because when the cache line of this core has data update, the cache line in other cores is set to invalid, so frequent cache misses are caused.

At this point, I believe that we have a deeper understanding of "java cpu cache coherence on programming what help", may wish to actually operate it! Here is the website, more related content can enter the relevant channels for inquiry, pay attention to us, continue to learn!

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