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From Steve Loughran <ste...@apache.org>
Subject Re: Is there any performance issue with Jrockit JVM for Hadoop
Date Thu, 07 May 2009 15:35:47 GMT
Chris Collins wrote:
> a couple of years back we did a lot of experimentation between sun's vm 
> and jrocket.  We had initially assumed that jrocket was going to scream 
> since thats what the press were saying.  In short, what we discovered 
> was that certain jdk library usage was a little bit faster with jrocket, 
> but for core vm performance such as synchronization, primitive 
> operations the sun vm out performed.  We were not taking account of 
> startup time, just raw code execution.  As I said, this was a couple of 
> years back so things may of changed.
> 
> C

I run JRockit as its what some of our key customers use, and we need to 
test things. One lovely feature is tests time out before the stack runs 
out on a recursive operation; clearly different stack management at 
work. Another: no PermGenHeapSpace to fiddle with.

* I have to turn debug logging of in hadoop test runs, or there are 
problems.

* It uses short pointers (32 bits long) for near memory on a 64 bit JVM. 
So your memory footprint on sub-4GB VM images is better. Java7 promises 
this, and with the merger, who knows what we will see. This is 
unimportant  on 32-bit boxes

* debug single stepping doesnt work. That's ok, I use functional tests 
instead :)

I havent looked at outright performance.

/

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