[concurrency-interest] ConcurrentSkipListMap performance

Mohan Radhakrishnan mohanr at fss.co.in
Thu Nov 10 06:33:13 EST 2011

I found this a section on 'Compilation' in http://www.cs.princeton.edu/picasso/mats/HotspotOverview.pdf that has some details.






From: concurrency-interest-bounces at cs.oswego.edu [mailto:concurrency-interest-bounces at cs.oswego.edu] On Behalf Of Nathan Reynolds
Sent: Tuesday, October 25, 2011 9:46 PM
To: Thorsten Möller
Cc: concurrency-interest
Subject: Re: [concurrency-interest] ConcurrentSkipListMap performance


I turn on HotSpot's -XX:-PrintCompliation and run the warmup and test.  If I see any messages during the actual test (after warmup), then I know I didn't warmup the JVM long enough.

The parameter -XX:CompileThreshold (i.e. optimizer threshold) defaults to 10,000 when using the "-server" flag.  I find that if I run the method under test and all of the test harness code 11,000 times then I don't see any compiler (optimizer) messages during my test.  I also put a Thread.sleep after warmup but before running the test.  This gives time and CPU resources to the compiler (optimizer) threads.

Getting this right was very tricky.  I am still not confident that I have mastered it yet.  I should really do some harness tests to gain more confidence.

Nathan Reynolds <http://psr.us.oracle.com/wiki/index.php/User:Nathan_Reynolds>  | Consulting Member of Technical Staff | 602.333.9091
Oracle PSR Engineering <http://psr.us.oracle.com/>  | Server Technology

On 10/25/2011 2:13 AM, Thorsten Möller wrote: 

Am 24.10.2011 um 22:20 schrieb Nathan Reynolds:

	Note:  HotSpot does have an optimizer logging feature and can be used to determine if the optimizer is finished (i.e. by lack of further output).

Interesting - wasn't aware of this yet. Could you detail how it can be used. Seems that it is a JVM parameter [1]?
[1] http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html
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