Learn memory management of JVM 01 - first memory

Catalog

The meaning and function of memory

Why is memory faster

About caching

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From this one on .

Java virtual machine ——JVM Kicked off .

The main content of this article is a brief introduction to memory . And JVM irrelevant .

Computers have internal and external memory . External memory is our hard disk , Data and programs are stored in hard disk . If stored in memory , Shut it down and it should be gone .

In order to realize the calculation function , You need to put the data in the hard disk , Deliver to CPU. That is to say, the design of computer needs to realize the following process ：

This transmission process can be realized in theory . But our actual transmission is as follows ：

Why is that ？ What is the meaning and function of memory ？

The meaning and function of memory

because CPU Computing data is much larger than reading and writing , direct External memory is transferred to CPU It will cause a lot of time to wait .

Memory reads and writes faster , And with the memory buffer , It can continuously transfer the data in the hard disk to the memory , Waiting to be used .

Why is memory faster

The storage form of memory is capacitance , Can read and write very fast .

Capacitors store charge , high voltage representative Binary 1 Low voltage representative 0

Realize analog circuit - > digital circuit ： To make a 0 、1 Express

The knowledge about analog circuit and digital circuit belongs to the principle of computer composition , Don't go over here .

About caching

Caching is also to reduce CPU The waiting time of .

CPU Have three-level cache promotion CPU Interaction speed with memory .

for instance , hold Variable a Do it ten times a++

There are two ways at this time

1. Do it once +1 Then give it back to memory , Retake , add .

2.   direct 10 Time +1, Return the final result .

Obviously the second is faster , Caching is the condition for the second way .

Okay , That's all for this article

Keep early hours , take care . King of early rising , I wish you good luck .