Here are my results (Athlon 900, 512MBRAM, development machine, windows, jdk 1.3, 
running in IDEA):

buffered: false, immediateFlush: true, avg log time: 141.8 in microseconds.
buffered: false, immediateFlush: true, avg log time: 145.01 in microseconds.
buffered: false, immediateFlush: true, avg log time: 150.41 in microseconds.
buffered: false, immediateFlush: true, avg log time: 152.01 in microseconds.
buffered: false, immediateFlush: true, avg log time: 153.82 in microseconds.
buffered: false, immediateFlush: false, avg log time: 128.98 in microseconds.
buffered: false, immediateFlush: false, avg log time: 133.09 in microseconds.
buffered: false, immediateFlush: false, avg log time: 139.6 in microseconds.
buffered: false, immediateFlush: false, avg log time: 141.0 in microseconds.
buffered: false, immediateFlush: false, avg log time: 142.7 in microseconds.
buffered: true, immediateFlush: false, avg log time: 125.28 in microseconds.
buffered: true, immediateFlush: false, avg log time: 129.28 in microseconds.
buffered: true, immediateFlush: false, avg log time: 130.49 in microseconds.
buffered: true, immediateFlush: false, avg log time: 133.19 in microseconds.
buffered: true, immediateFlush: false, avg log time: 135.89 in microseconds.

Regards,

Mathias

------------------------
 "Log4J Developers List" <[EMAIL PROTECTED]> wrote:
------------------------
Hello all,
>
>
>As you probably know, performance of buffered IO is supposed to be
>much much better then non-buffered IO. In around mid 2001, we had a
>discussion about buffered IO and although buffered IO is supposedly
>faster my own tests showed that when outputting logs (write only
>operation) this was not the case. There were no performance gains that
>could be observed. Note that all the articles and books discussing
>buffered IO carry out read-only tests without any writing. So since
>performance gains could not be verified independently, we did not add
>buffered IO functionality to log4j.
>
>In early 2002, a user (I can't find the name since Bugzilla is down)
>filed a bug report claiming that on a heavily used server machine
>adding buffered IO to FileAppender gave a perceptible boost to logging
>performance.  As a response we added buffered IO to FileAppender.
>
>The problem is that I sill can't see any 10 fold improvements that
>some tuning experts assign to buffered IO.
>
>Here is a short test file that tests the performance of
>FileAppender. It uses multiple threads to imitate a
>"heavily" loaded server.
>
>import org.apache.log4j.*;
>
>public class IO extends Thread {
>
>   static String msg = 
>"ABCDEGHIJKLMNOPQRSTUVWXYZabcdeghijklmnopqrstuvwxyz1234567890";
>   static int BUF_SIZE = 1024*4;
>
>   public static void main(String argv[]) throws Exception {
>
>     // What is the length of the runs?
>     long len = Integer.parseInt(argv[0]);
>
>     boolean buffered;
>     boolean immediateFlush;
>     IO io = null;
>
>
>     // first test with unbuffered IO and immediate flushing
>     buffered = false;
>     immediateFlush = true;
>     for(int i = 0; i  javac IO.java
>  ~/ > java IO 100000
>buffered: false, immediateFlush: true, avg log time: 91.94 in microseconds.
>buffered: false, immediateFlush: true, avg log time: 94.94 in microseconds.
>buffered: false, immediateFlush: true, avg log time: 97.04 in microseconds.
>buffered: false, immediateFlush: true, avg log time: 96.44 in microseconds.
>buffered: false, immediateFlush: true, avg log time: 99.74 in microseconds.
>buffered: false, immediateFlush: false, avg log time: 67.1 in microseconds.
>buffered: false, immediateFlush: false, avg log time: 73.21 in microseconds.
>buffered: false, immediateFlush: false, avg log time: 72.61 in microseconds.
>buffered: false, immediateFlush: false, avg log time: 74.21 in microseconds.
>buffered: false, immediateFlush: false, avg log time: 76.11 in microseconds.
>buffered: true, immediateFlush: false, avg log time: 61.79 in microseconds.
>buffered: true, immediateFlush: false, avg log time: 63.99 in microseconds.
>buffered: true, immediateFlush: false, avg log time: 68.1 in microseconds.
>buffered: true, immediateFlush: false, avg log time: 70.1 in microseconds.
>buffered: true, immediateFlush: false, avg log time: 71.0 in microseconds.
>
>
>As you can see, immediate flushing has an impact on performance whereas
>buffering does not. The test was run on Windows (JDK 1.2.2, 1.3.1) and
>Linux (JDK 1.4.0) with very similar outcomes.
>
>Is it possible that the experts are wrong? Could you run the test on
>other platforms and post the results here? (The whole shebang takes
>about 5 minutes.) Many thanks in advance,
>
>
>--
>Ceki
>
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>
>
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