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Re: DataOutputStream performance under OS X

Jussi Hagman <email@hidden> wrote:

>Maybe so, but when writing at 12kB/s the program is also using every
>CPU-cycle available so perhaps it would be a bit faster with a faster
>CPU...

A faster CPU will not make nearly as much difference as using the Java I/O
classes well.

That usually means placing a BufferedOutputStream between a
FileOutputStream and anything else writing to it. That may mean tuning
buffer-sizes, too. I usually start with 4K, but you may be happy with the
1/2-K default.


>However, if I understood correctly this is as it it is supposed
>to be.

It's not "supposed to be" any particular way. It's just that it can vary
across platforms, depending on implementation. Apple implemented it one
way. Sun implemented it another way. Both are correct, and both are
"supposed to be" exactly what they are: different implementations.


>Thankfully I do not have the need to use Java at the moment. If
>the need arises it seems that I'd probably be better off with another
>operating system.

You'd be much better off learning to use the Java I/O classes well.

When I ran your tests on my machine, I measured a 150X difference in speed
between the buffered BOSTest (82 ms) and the unbuffered DOSTest (11952 ms),
after I added code to measure elapsed time. To satisfy my curiousity, I
wrote a FOSTest that calls FileOutputStream.write(int), too. As expected,
it is essentially the same speed as DOSTest, since neither one performs any
additional buffering.

I suspect most of the BOSTest's elapsed time is spent creating the files,
not writing to them. 6 files in 82 ms is only about 13 ms each, and
file-creation is always unbuffered, so you have no control over that. But
you have quite a lot of control over how you use the I/O classes.

-- GG
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