On Thu, 2005-01-20 at 10:12, Ceki GÃlcà wrote:
> Elias,
>
> Thank you for your proposal. Would it possible for you to backup your
> proposal with prototype code? I'd be very interested in a comparative
> study between an Appender using the current concurrency model and an
> Appender following your improved model. A performance test involving
> several threads would be quite appropriate.
>
> (Appender is an interface so one can easily swap implementations.)
>
> How does that sound?
Sounds fantastic.
I wrote some simple tests. Here's some of the code using the old
interface and the new one.
ConcurrentAppender ca = new ConcurrentAppender() {
protected void append(LoggingEvent event) {
try { Thread.sleep(1); } catch (InterruptedException e) {}
}
protected void internalClose() {}
};
AppenderSkeleton as = new AppenderSkeleton() {
protected void append(LoggingEvent event) {
try { Thread.sleep(1); } catch (InterruptedException e) {}
}
public void close() {}
};
Using 5 threads with 100 log statements, here's what I got (a representative
sample):
[java] AppenderSkeleton
[java] Appender class org.apache.log4j.concurrent.PerformanceTest$2
[java] Took 1066ms for 100 logs * threads 5
[java] ConcurrentAppender
[java] Appender class org.apache.log4j.concurrent.PerformanceTest$1
[java] Took 288ms for 100 logs * threads 5
It's about 3-4 times as efficient.
Is there some place to put a patch?
I also wrote new ConsoleAppender, WriterAppender versions. They perform
about the same as the old ones on a single processor machine, which
isn't a surprising finding, but it's good to know they are just as fast.
One thing I noticed was that Layouts were not thread-safe. Most of the
code time is spent in that class *. I changed the PatternConverter
class signature from:
protected abstract void convert(LoggingEvent event);
to:
protected abstract void convert(StringBuffer sb, LoggingEvent event);
and rewrote Layout in such a way that it is thread safe. Obviously,
there would be compatibility issues, which is why I am thinking of
creating a separate Layout class to be used in this way.
* According to my last run 87% of the CPU time was spent formatting. So
if you have 2 CPUs, 87% of the other CPU's time is waiting!
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