12.1.0 - Allow configuring minimum size before File Mapped Buffers are used.

[joakime]

Jetty version(s)
12.1.0

Enhancement Description

There are several places we use the FileChannel.map() feature to load File as a memory mapped ByteBuffer.

• https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/channels/FileChannel.html#map(java.nio.channels.FileChannel.MapMode,long,long)

The javadoc for this method indicates the following memory concern ...

"For most operating systems, mapping a file into memory is more expensive than reading or writing a few tens of kilobytes of data via the usual read and write methods. From the standpoint of performance it is generally only worth mapping relatively large files into memory."

The enhancement is that there should be a configurable minimum size before a memory mapped ByteBuffer is used, vs a normal ByteBuffer from typical file I/O operations.

Discovered as part of issue #12695