ReentrantLock performance regression between JDK5 and 6/7?

[Clemens Eisserer]

Hi Vitaly,

I tried this bench on 6u23 and if I first run that code in a 10k iteration
> loop and then time the 1mm iteration loop I get about 10 ms speedup.  The
> first loop would trigger jit compilation (10k is the default threshold I
> believe) and second should run without compilation interruption.
>
> Can you try the same? Also might be interesting to time it under the
> interpreter (-Xint).
>
I changed the testcase a bit, to no longer rely on OSR - as lockBench() will
for sure soon hit the compilation threshold after a few runs.

I get the following timings for 1m runs:

jdk7-server: 53ms
jdk7-client: 62ms
jdk7-xint  : 955ms

jdk6-xint  : 1000ms
jdk6-client: 68ms
jdk6-server: 52ms

jdk5-server: 40ms
jdk5-client: 61ms
jdk5-xint  : 832ms

So JDK7 is slower in every case, the regression seems to have landed in jdk6
(I was using openjdk6).

Should I file a bug-report about this behaviour?

Thanks, Clemens


public class LockPerf {
    static ReentrantLock lock = new ReentrantLock();

    public static void main(String[] args) {
     while (true) {
          long start2 = System.nanoTime();
          for(int i=0; i < 1000; i++) {
          lockBench();
        }
        System.out.println("Lock bench: " + ((System.nanoTime() - start2)) /
1000000);
    }
    }

    private static void lockBench() {
        for (int i = 0; i < 1000; i++) {
          lock.lock();
          lock.unlock();
        }
    }
}



> On Aug 11, 2011 11:38 AM, "Clemens Eisserer" <linuxhippy at gmail.com> wrote:
> > Hi Vitaly,
> >
> > Which OS are you using?
> >>
> > Linux-3.0 (Fedora 15)
> >
> >
> >> Also, you should use System.nanoTime() for this type of timing as it
> gives
> >> you a more precise timer.
> >>
> > I tried, but results remained the same. ~53ms for jdk6/7, ~41 for JDK5.
> > I was using the server compiler both times.
> >
> > Thanks, Clemens
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/attachments/20110811/4c947adc/attachment.html