Re: NIO not so hot

From:

Robert Klemme <shortcutter@googlemail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 18 May 2014 19:09:13 +0200

Message-ID:

<bts7pqFne9dU1@mid.individual.net>

On 18.05.2014 14:12, Robert Klemme wrote:

On 18.05.2014 13:38, Robert Klemme wrote:

https://gist.github.com/rklemme/fad399b5e7cc4d3b6d0c

PS: I just notice some oddity with the ASCII file size which is too
small. I need to check that.

Error was duplicate counting chars during creation. This is fixed now.

I rearranged execution order a bit to group all read operations on one
file and all NIO reads with direct or heap buffer.

https://gist.github.com/rklemme/fad399b5e7cc4d3b6d0c#file-output-txt

My takeaways:

  - IO and NIO have roughly same performance for char decoding
    if done properly.
  - Adding byte buffering to IO does not help, rather it makes
    things slower.
  - Reading into char[] with IO is more efficient than using
    char buffering.
  - NIO direct buffers are slower than heap buffers; they are
    probably best used if the data does not need to reach
    the Java heap (e.g. when copying a file to another file
    or a socket).
  - Best performance with NIO is with a multiple of memory page
    size (or file system cluster size?).
  - decoding of pure ASCII in UTF-8 is much more efficient
    than random UTF-8 data (over 4 times faster per byte than
    the mixed UTF-8 file).

ASCII 0,001525879 us/byte and char
UTF 0,006485037 us/byte
UTF 0,019073486 us/char

Cheers

    robert