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javamappedbytebufferoff-heap
Jenson
Jenson

Reputation: 87

Java-Does mappedbytebuffer occupy direct memory?

I am curious whether the mappedbytebuffer occupies direct memory in Java? As mentiond in here

A direct byte buffer may also be created by mapping a region of a file directly into memory

When I map a file into memory, the direct memory should be used. But I started a program with JVM param "-XX:MaxDirectMemorySize=200MB" then I tried to map a file of 1GB into memory, it worked. What's more, I allocated a directByteBuffer with 200MB first and then tried to map the file of 1GB into memory, and it still worked! So, which part of the memory does mappedbytebuffer occupy?

Upvotes: 1

Views: 534

Answers (1)

chen wen qing
chen wen qing

Reputation: 11

i think,when you map a bigger file into small memory, the instance of mappedbytebuffer may mapping a region of a file which you have just used into memory ,then the other region which have been map in memory will exchange into SWAP(the virtual memory on hard disk ) by MMU

Upvotes: 1

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