Home/ Questions/Q 8589417
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-11T23:03:11+00:00

My Java application deals with large binary data files using memory mapped file (MappedByteBuffer,

  • 0

My Java application deals with large binary data files using memory mapped file (MappedByteBuffer, FileChannel and RandomAccessFile). It often needs to grow the binary file – my current approach is to re-map the file with a larger region.

It works, however there are two problems

  1. Grow takes more and more time as the file becomes larger.
  2. If grow is conducted very rapidly (E.G. in a while(true) loop), JVM will hang forever after the re-map operation is done for about 30,000+ times.

What are the alternative approaches, and what is the best way to do this?

Also I cannot figure out why the second problem occurs. Please also suggest your opinion on that problem.

Thank you!

Current code for growing a file, if it helps:

(set! data (.map ^FileChannel data-fc FileChannel$MapMode/READ_WRITE
                         0 (+ (.limit ^MappedByteBuffer data) (+ DOC-HDR room))))
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You probably want to grow your file in larger chunks. Use a doubling each time you remap, like a dynamic array, so that the cost for growing is an amortized constant.

    I don’t know why the remap hangs after 30,000 times, that seems odd. But you should be able to get away with a lot less than 30,000 remaps if you use the scheme I suggest.

    • 0