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From Scott Carey <sc...@richrelevance.com>
Subject Re: Sun JVM 1.6.0u18
Date Mon, 01 Mar 2010 23:41:08 GMT

On Mar 1, 2010, at 10:46 AM, Allen Wittenauer wrote:

> On 3/1/10 7:24 AM, "Edward Capriolo" <edlinuxguru@gmail.com> wrote:
>> u14 added support for the 64bit compressed memory pointers which
>> seemed important due to the fact that hadoop can be memory hungry. u15
>> has been stable in our deployments. Not saying you should not go
>> newer, but I would not go older then u14.
> How are the compressed memory pointers working for you?  I've been debating
> turning them on here, so real world experience would be useful from those
> that have taken plunge.

Been using it since they came out, both for Hadoop where needed and in many other applications.
 Performance gains and memory reduction in most places -- sometimes rather significant (25%).
 GC times significantly lower for any heap that is reference heavy.  Heaps are still a little
larger than a 32 bit one, but the benefits of native 64 bit code on x86 include improved computational
performance as well.  6u18 introduces some performance enhancements to the feature that we
might be able to use if 6u19 fixes the other bugs.  The next Hotspot version will make it
the default setting, whenever that gets integrated and tested into the JDK6 line.  6u14 and
6u18 are the last two JDK releases with updated Hotspot versions.
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