[IO-468] Avoid allocating memory for method internal buffers, use threadlocal memory instead

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Won't Fix
• Affects Version/s: 2.4
• Component/s: Utilities
• Labels: newbie performance

Environment

all environments

• Assignee: Unassigned
• Reporter: Bernd Hopp
• Created: 03/Feb/15 07:50
• Updated: 17/May/18 09:29
• Resolved: 09/Mar/15 00:48

Description

In a lot of places, we allocate new buffers dynamically via new byte[]. This is a performance drawback since many of these allocations could be avoided if we would use threadlocal buffers that can be reused. For example, consider the following code from IOUtils.java, ln 2177:

return copyLarge(input, output, inputOffset, length, new byte[DEFAULT_BUFFER_SIZE]);

This code allocates new memory for every copy-process, that is not used outside of the method and could easily and safely reused, as long as is is thread-local. So instead of allocating new memory, a new utility-class could provide a thread-local bytearray like this:

byte[] buffer = ThreadLocalByteArray.ofSize(DEFAULT_BUFFER_SIZE);

return copyLarge(input, output, inputOffset, length, buffer);

I have not measured the performance-benefits yet, but I would expect them to be significant, especially when the streams itself are not the performance bottleneck.

Git PR is at https://github.com/apache/commons-io/pull/6/files

Issue Links

• links to: GitHub Pull Request #6